In a 3C, you can get the same or more energy as 2p 18650s by simply using 3s NiMH C cells. The same if you go for low-self discharge cells 4500mAh cells from Thomas distributing. More if you go for standard 6Ah cells.
Another advantge of NiMH cells is that they can be safely series charged without balancing taps, so you could actually install a DC power jack up near the switch, and charge the NiMH cells IN the light.
I realize this, but would like to semi standardize my batteries. I don't really care if i have to take them out to charge them. Also, since batteries come in pairs, it's really more economical for me.
EDIT: I also dont have a decent charger for C cells. So it would cost me $100 to keep it C since i would get the maha 8 cell charger if i go that route. This solution is really temporary untill i can afford the c cells and charger i guess.
I have the tube and wireing, but need an idea on how to connect the ends. I'm thinking screwing caps of some kind or, like
nein166 suggested, make it side load. The only thing i have against side load is that right now i have it 100% rattle free. I ended up machining it out of a piece of solid rod. I wasn't happy with the results of using pvc(batteries were loose and rattled to much for my liking.
Thanks