I got the XPG-R5 5-mode. I was also thinking of getting the MC-E but the donut hole or plus sign showing in the center of the beam wasn't very attractive.
This is the link: http://www.kaidomain.com/ProductDetails.aspx?ProductId=10068
Oh, I thought you ordered just the drop-in but I see it's a UltraFire WF-501B 3.7V~4.2V CREE XPG R5.
Yeah, I'm just going to take the drop-in and put it in the Solarforce. The drop-in, if bought separately costs more than the whole thing, unless I'm not searching correctly: http://www.dealextreme.com/details.dx/sku.32954 I'll have an extra body for other uses.
FWIW, I've had no problem with my 5 mode dropin from LT that came with my fake Solarforce body. It appears to be the same dropin as the Skyray on DX from the pictures (I thought this before buying it) and does have a smooth reflector. I think the XPG dropin DX sell seperately is the same (it looks it) The current draw is a little les then I hoped, seems to be about 1A on single 18650 or similar with 3xNiMH. Of course current draw drops as the voltage goes down. Current draw on 2x18650 is about 0.45A or so IIRC. I've added aluminium foil and while the head gets warmish, heat seems okay, even after say 2 hours the pill is just warm, and not too hot to touch. I did try connecting it to the 5V of a computer PSU for a while without the body or head and it does get too hot to touch so I didn't try that again :-P (Later connected it to the body & head and it was fine.)
I must have run it for at least 12 hours by now in various testing as well as some cycling.
I did find the body is a bit too long particularly with 1x18650 (black/red flame) so the battery rattles, back and forth (also side to side but this is easily solvable). This may seem annoying but harmless enough, it did to me at first except it means it keeps switching mode when I'm cycling and go over bumps (primarily when the back wheel comes off a bump). Mind you, from what I gathered in my research, quite a few genuine Solarforces have a similar issue. There's a slightly possibility I damaged my spring somewhat causing the issue (long story, will explain in more detailed review) but I think it's just the body is too long or the springs aren't long enough. With 2x18650 while I can change mode by shaking the light, when I went cycling with this combo once it didn't seem to switch by itself. With 2x18650 you can just put a spacer like aluminium foil between the batteries and then tape them together, they get a bit sticky but the foil won't short. With 1x18650 I stuck a piece of foil in the spring and it seemed to work. One or more of those rear earth magnets people often use as magnets is probably the best solution.
I received my 501B R5 drop in from KD yesterday. The quality of the 501B host is way lower than quality of the real Solarforce. I tested the 501B for fun but it had contact problems. When everything is screwed down tight, the flashlight wouldn't turn on. I had to loosen the head and it turned on. It also seems like the big spring of the pill is being compressed too much. When I tightened down the head, I could hear crunching down of the spring.
After trying the 501B body, I transferred the drop-in to the Solarforce body. Fights perfectly and no spring crunching noise when I tightened the head. There is sort of a rattle if I shake the light violently but the modes do not change.
It's a pretty bright light. Pulling 1.3A at the tailcap on a 4.10V 18650 battery. The beam profile looks very similar to my Hugsby P31, but it's about 2.5x brighter and has more of a cooler/whiter tint. It doesn't throw as well as my KD MXDL 18650 but that light is zoomable 
Overall I'm happy with the DX R5 drop-in/ITC Solarforce combo. Now I want something brighter 
Any suggestions?
And how silly money are you prepared to spend?
If prepared to spend a lot go to www.lambdalights.com - Varapower V2000 or www.elektrolumens.com - especially the Kong. The Kong is around $1500 and 11,000 lumens. It uses TWELVE 18650s. It is 18" long and the head is about 5" in diameter. Just don't be in a hurry for it, Wayne does good work but takes his own sweet time about it.
The Varapower is rather more sensible at around $200 and 2,000 lumens. I am biased about Varapowers as the one in the pics now belongs to me.
On a saner note, the Romisen RC-T6 is well worth a look, likewise the 5 LED TR-1200. One of the better P7 lights (one that uses 2 18650s) or an SST-50 would give a lot of light. LighTake have a Trustfire SST-50 at $63 including their 10% discount. Since this is $6 more than DX want for the RC-T6 and is probably way brighter (Though not 1300 lumens I'd be certain) it looks like a pretty good deal to me. DX want $76 for the same thing
DX do an SST-50 P60 dropin for $39 but heatsinking and current draw make it a poor idea especially as at DX' claim it is only a little brighter than their hard-driven MC-E dropin that comes with a free 501B body.
There is no point in an SST emitter if it isn't driven at the amps it wants (5A for an SST-50 (around 12-15W), 9A for an SST90 (Around 30-35W) and 36A for an SST-360 which is 4 SST-90's on one chip - or about 120-150 watts (And costing around $90 for the LED). These LEDs are designed for projectors with lots of fans to keep them cool.
Something like 20 18650s in a 5p 4s configuration ought to do the trick for a bit under an hour. Bit bulky though and there will be the 80-odd watts of heat to lose. Bulk and cooling might be a problem - not to mention runtime and forget reflectors of less than a foot in diameter to handle the hole in the middle
Hey Don, do you have an SST-50 or an SST-90 drop-in or both? I was thinking about getting one for my extra Solarforce L2m body since I have the 18650 extender and can use 2 - 18650's? Any experience with either one of the SST-50 or SST-90 drop-in's? Thanks. 
SST-50/90 LEDs need more current than most P60 lights can deliver. Personally I'd be looking for 3x18650 or more in parallel to deliver the sort of currents these guys need. The DX SST-50 P60 isn't worth it for the claimed lumens. The bare minimum I'd suggest is the Lightake SST50 which I reckon to be a good deal at $63. And I'd probably prefer the $120 one with 3x18650 in parallel. An SST-50 probably costs around $15 wholesale and reckon on >100% markup retail.
But I could be wrong - it wouldn't be the first time. Not about to spend the money to find out though. The DX MC-E in the 501 body which I got is probably brighter for the same or less money - but I got a good one, brted didn't. At those sort of prices you are in a lottery with very low odds of winning.
I saw that nailbender on CPF was selling some and thought about getting an SST-50 or SST-90 drop-in from him. They are very expensive but it looks like they are very well made and reliable. He also sells a lot of other different kinds of P60 drop-in's among other things. Anyone here have any experience with nailbenders products? Thanks.
I'm with Don on not putting a SST-50 or -90 in a P60 host. 1 or even 2 18650's isn't going to do them justice and once you start giving them the juice they need you start having to deal with a LOT of heat. Even a P7 or MC-E in a P60 is really pushing it and those need about half the amperage of a SST-50. I have a heavy duty 2x18650 P7 light where a really big brass pill screws into a heavy aluminum throat with some decent heat-dissipating ridges and that thing gets pretty hot after about 5 or 10 minutes. I can put an ice cube on the ridges and it melts in a few seconds, so the thermal path is awesome on that thing. An SST-50 would make twice as much heat . . . ?
The one thing the SST has going for it is it won't have a donut hole in the beam. So if you are under-driving it you could still get a very bright light (though no more so than a P7 or MC-E), a nicer beam, and a sane amount of heat to deal with.
Does a P7 have the donut hole like the MC-E?
Yes - the dies for them are made by Cree. The difference is SSC use a different phosphor, lens and goop inside the lens.
However getting rid of the hole is mostly a matter of careful design and manufacture. Or defocussing the reflector a bit.
Many believe the P7 to have better beam quality than the MC-E
Thanks guys! Maybe I'll just get one of SBFlashlights Thrunite drop-in's or I might just get a cheap one from DX.
Do you guys know where I can buy a tailcap for my Solarforce L2 in gunmetal gray color so that it can tailstand?
It's not gunmetal colour, but if you can live with silver colour this might be the cheapest option . I suppose the threads are compatible, better ask brted first.
Here's a picture with the 504B tail on the L2. It's not terrible. I was worried the threads weren't compatible, but I think it was just some resistance I was getting when the tailcap got to the o-ring. It leaves a gap, but the tail switch works. (click the picture for a bigger version):
Thanks Vectrex and brted. Looks odd but not too bad with the 504B tail. Maybe I'll just get the 504B and have an extra light :)
Unfortunately the new bodies that Solarforce is putting out ironically reverses any benefit it had over the clones. The body is flat, the color less olive (doesn't even match the bezel!), and pretty much every clone feels better in the hand. Sigh.