It turned out that the head was extremely easy to disassemble - I just used 2 of those super-grippy cloths used in the kitchen to open tight jars and a bit of brute force
Will buy an R2 led and solder it up tomorrow, could I reasonably expect around 170 torch lumens? I recall it puts out about 110-120 torch lumens on the 14500 using the P4 with just under one hour runtime
Update: Well, while the head was easy to disassemble, soldering the actual emitter was a royal pain in the... Finally got it working tho, noticeably brighter and a warmer tint... =)