this is a good way of doing it, I always thought I need chemicals and good luck. Never done it before… thanks for this.
Just a reminder, you have to make sure that you get all the residue off of the led after sanding it down or you will have a meltdown of the led. I burned up 2 leds like this, and now I have a smoked reflector to show for it on my convoy c8+. Luckily I have an extra reflector lying around and more leds to use.
Will an ethyl alcohol bath suffice?
That didn’t work for me. I did that for both the leds, the second one I did for longer and it still burned. This time around I’m going to use an air can to blow everything off and put a little bit more elbow grease using a qtip and alcohol.
What do you mean when you say the led burns?
Insight tells me this has to do with minuscule dome debris pieces being somehow pre-melted due to the very own abrasive sanding process, and this very stuff sticking somewhere and causing trouble due to alcohol not being able to really dissolve dome material.
Tip: use a bit of gasoline or white spirit for the next-to-last coating, then finish with alcohol.
I didn’t have problems with the sst-40, but the 351d’s were problematic after sanding it down. Even after I thought I thoroughly cleaned it some residue burned on the led when I turned it on and there were burn spots on the led. I’ll try your suggestion when I get my new order of 351d in.
Update.-
Ended up dedoming a couple XHP50As via razor blade plus fine grit sandpaper method. First one worked at first, but upon heating up installed in a modified SK98 half the emitter was turning off. I believed this was caused by going too low with the dome removal, thus for the next emitter I made sure to not go below 1.1mm. For this second one I sanded down the thing much more, until I noticed the actual emitter killer: the sanding movement messes up fatally with the bond wires à la domequake. 
For a final round I'm gonna go slow (fridge temp) chemical dedome with white spirit, a method which works wonderfully with XM-L2s, leaving dome remnants protecting the bond wires. If this does not work I'll throw in the towel.
Cheers :-)
I will tell you guys that you should not be afraid for your bond wires after nice clean chemical de doming.
So for your peace of mind I’ve done hundreds of dd lights for hunters (mounted and used on high recoil centerfire rifles), and I did not had a single emitter fail (I had electronics fail or switch fails but not emitter).
I had some bad experiences also… Sometimes I was impatient leaving some micro residue on emitter and then after turning on the flashlight I could just watch how emitter goes from nice white to angry blue 
That happened to me several times. If some micro spec of dirt or similar fells on de domed emitter it will kill it for sure.
So if you have any speck of dirt on emitter just rinse emitter with isopropyl alcohol and blow with compressed air.
Oh! Well, I immersed the semi-failed razor blade dedomed XHP50A in white spirit. After a day in the spirit the emitter wasn't even turning on. XHP50As and XHP70As are dedoming bitches. I may still try carefully with a sanding bit equipped Dremel style tool. 
^:)
I have sanded my dedomed LEDs as well, after I saw this thread. I have used lapping sheets also.
Maybe, this is the best picture from the below thread:
My dedomed LEDs are in that thread (picture heavy): Cheap chinese lamp dedoming pictures.
The LED came out nice, great job.
Thank you!
I hope I will do the same great job with XHP 50.2 and 70.2. Those are a “little bit” more expensive than these 
Had to ask there, hope RelakS can share his sanding method because I gave up on it after killing a couple XHP50A emitters.
Sanding method? 
I haven’t done anything special. I put some tiny amount of water to the sand paper, and moved the LEDs back and forth on it, without much pressure.
I also have checked the progress frequently, because I did not want to end up with the bare LED base
I think that the most important is to leave enough material from the dome to sand down. Maybe tomorrow I will do the same with an XHP50.2, I will see how it turns out. If an XHP70.2 is enough to have 1mm high cut, than for sanding, maybe 1.1mm or 1.2mm will be necessary.
Probably would be wise to use a washer that is the desired thickness as a spacer. Put the MCPCB upside down over the washer so that the LED sticks through it and the washer keeps you from sanding too far. Also would keep the LED flat against the sand paper while sanding.
Almost no pressure and wet sanding
Mmmkay, so you're speaking of super O:) gentle, slow sanding. That must be a lot of sanding time, doesn't it? 
Washer, os some flat metal, which you stick to the same base where the LED is. I use washers as spacers to cut the dome to begin with
The problem is that if a washer is big enough to stick through the LED, or to drill a nice hole in it, it is usually too thick, so I put two small washers next to the LED.
silicone is very soft and not much area to be sanded so no
XHP70.2 next gen
unfortunately on one side a bit silicone broke off
