Dropins for solarforce are much more of a tube (very straight), malkoff dropins fit better in a surefire (or obviously a md2 from malkoff) which has a tapered "throat" that fits the malkoff/oveready and many others. At a minimum wrap the bottom until you get a tight fit. It's obviously better to wrap it in o get contact everwhere for heat transfer.
i'm traveling, so I don't have acc ss to my lughts, but I do have a solarforce custom dropin from vinz (Germany) and the shell is quite different from a surefire style dropin.