I just realized that the dropin that I installed in my Pelican M6 is a Solarforce .6-4.2v XP-G
I have been using it for the last couple weeks with a pair of CR123 batteries (since 18650 batteries do not fit in the Pelican body). It didn't seem any worse for the wear, but it is brighter with a 4.2v than it was with 2c Cr123's.
Oops.
I did that on purpose a few weeks ago with the 3-mode Ultra Fire XM-L drop-in. Put two fresh Energizer CR123s in an L2 and turned it on high. I can't find the thread, I don't know if I started it or not. I thought I had ruined it but it's fine. I might have impacted its life span . . .
I turned it on high for about 15 minutes I think. (wish I could find the thread - I'm tired) It dimmed, got real hot then cooled. Can't remember the whole thing but it's probably a crap shoot; meaning if it still works it may not be because it's okay to do it, you just got lucky.
Foy
Everything seems OK. The weird thing is that the Solarforce dropin was one of the few I have that is clearly labeled from the factory with type and voltage and modes. All I had to do was read that darn thing...
If I recall correctly that dropin Foy hit with too much voltage appeared the brightest in a later set of beamshots he did. Not that that experiment made it brighter, just didnt seem to hurt it.
It should be ok. If you think about it they make dropins in different voltage ranges. And that is controlled by the driver. The LEds are the same no matter what voltage range dropin you get. If anything you’d have killed the driver.