Millerman,
Check out this thread I did awhile back.
https://budgetlightforum.com/t/-/7165#node-8370
I did the same thing to an old beat up 2C. It's a single xml driven off of one 18650 direct drive, along with every resistance mod I could come up with. Only thing is, the emitter is directly mounted to a big copper slug. I do have the battery recessed into the tailcap by using the stock spring cut down to fit(and wrapped with copper braid). Ditto on the switch. Bone stock save for a good treatment of DeOxit.
This particular light is my second most used light at work behind my H51. It's held up great.
Good luck with the build, and if you have any particular questions just hollar.