Umm, ok - I've done the XM-L2 U2 SinkPAD mods on both the BTU driver and DRY driver. Who is actually getting 4.5A on a DRY driver? Well, you can't, no way on XM-L2's on copper without doing some other things. You need to copper wire the battery carrier and use unprotected low resistance batteries. The DRY driver is a $5 driver and not worth a dime more than that: cuts out of high in 2 minutes, has poor PWM's in med and low modes. I've seen 4A on a DRY driver running XM-L2 U2's/SinkPAD's with the battery carrier mod'ed. There's the specs and then there's reality....
I'm really interested in seeing what they are doing exactly with these upgrades... Is it worth the $15? Oh sure, most likely. Will you get the improvements I get by custom mod'ing? I'm thinking not, no way, because of the poor high resistance battery carrier, fujik type of epoxy they use, no lapping, thinner wires, same drivers, etc. Actually I'm thinking the SinkPAD's with XML U3's would have been a nice option to offer stock because you could actually maintain the high amps and not have a big output drop over a short time, and still use protected cells.
Notice the posted specs still show the same amps and lumens #'s --- Ok, those lumens (3,500 on high) were never achievable stock, well proven by many. With the AR lens, it went up to 3,000 to 3,100 lumens. Full XM-L2/SinkPAD mod, we are seeing 3,500 - 3,800 lumens, 4,000-4,500+ on a direct drive driver (low resistance cells, advanced carrier mods). I'm guessing with the stock XM-L2 U2/SinkPAD version you will get 3,300-3,500 lumens, maybe. I measure 3.4-3.5A at the switch. If they didn't attempt to make other improvements, the amps will actually go down with XM-L2/SinkPAD's because of the Vf demand, so you don't get the full benefit. Think about it - 3 emitters, 3 cells - ratio is 1:1. so you got the same high Vf issues, and even with A DRY driver, you can't achieve high amps without all the other mods.
It's still a worth while upgrade, just don't expect too much from it. I don't see the getting the typical 20-25% out of it, in fact you may see as low as 10%, or less. With the BTU driver, I have actually seen as low as 10% even with additional mods - seems to vary quite a bit and that's why I'm now doing the Shocker mods with the IOS 3.5A driver.