if your thinking of building a drop in, why no take the next step, buy a host kit and build up a light designed for an xm-l, I’ve built a few lights now that are comparable to your average 18650 p60 sized light and even they heat up pretty quick at 3.5a.
At the end of the day, shoving 10+ watts into a nice little alu tube is always going to result in a hand warmer. 
Both fasttech and cnqg have a nice range of hosts now that result in extremely nice finished lights. I would personally choose the d5 host from cnqg matched to the qlite driver you mentioned, the result would be pretty close to nirvana.
here’s the build thread if your interested
I’ve been using this as my work edc since I vuilt it and its extremely robust, showing not a mark on it yet.