O-Light S-35 mod

Hey Just bought myself an o-light s-35 and am waiting for it to arrive. but as I sat there watching it track in the customs house, I thought to myself, would it be possible to mod it and get a replacement tailcap from o-light and use a 26650 cell instead of 3 AA batteries, And just keep the batterycarrier/tailcap for AA's as standby. Has anyone else thought of or tried this? I'm fairly certain the head can handle the voltage for a charged li-on at 4.2 since 3 Alki's would be pushing 4.5 at charged state. I know it wouldn't be brighter, but i'm sure it would be lighter and have twice the runtime of 3 eneloops, with a 4000mah cell. I'm gonna try and get a spare battery-carrier/tail cap assembly from olight and mod one of them, then i can answer the o-ring question if no-one else comes forward as having already tried it.

Comment's suggestions and other ideas for modding an s-35 are welcome, only catch is I'd prefer to keep it possible to swap out a carrier/tail cap so i can still use alki's in it.

Also has anyone else found out if the S35/S65 share a common head assembly?

The Olight S80 is exactly that... read the reviews though, the olight li ion battery has both + and - on the same end. so does the AA battery carrier from both the S35 and S65. you can't use a standard 26650 in a baton.