Ok IMRs are unnecessary but are they dangerous at all for ruining the light, or are IMRs just gonna give you lower capacity? Just wondering because Oveready only has 18350s in IMR
Using IMRs would only have a potential for danger if you use two of them and run the light until its output is severely dimmed....at which point the cells would be drained to well below 2.5 volts. It's possible that the cells could vent with flame, which is bad for the light, and the user. AW's hybrid IMR 3000 mAh 18650 cell wouldn't be much of a decrease in capacity, but there is no benefit from an output perspective in an AVS Bravo.
Is the length of 2 button top 18350s an issue in the Bravo? 65mm for the AW 18650 and 35mm for each 18350 buttons, that seems significantly longer. How about going with 1 18350 flat top and 1 18350 button top? Because you'll need at least one button in the middle to make contact with the 2nd battery, but the spring at the head is fine with flat top (save a little length). Anyway, IF 2x18350s would be causing me to really stuff them in tightly and strain the springs I'd rather not even use them at all because it would bother me to put extra strain on the springs and flatten them.
Two AW IMR 18350s are very slightly longer than one AW protected 3400 mAh 18650, but it'll work fine. It will take a bit more effort to fully tighten the tailcap, due to needing to fully compress the springs, but it's not excessive. This extra spring pressure may also slightly cave in the negative battery contacts, but it shouldn't have any negative side effects. I doubt two protected 18350s would work. I don't own any to test. One hybrid IMR 3000 mAh 18650, with the same length as an NCR18650B, is obviously shorter than two 18350s, and a bit shorter than a protected 18650, but it'll also work fine...because of the dual spring setup.
Mixing different cells in series is something to be completely avoided., so I wouldn't go the button top/flat top route.