I just got my Triton today. A vertical coil? That actually might be easier then the standard configuration as there is very little room in there to get very many wraps. I ended up using 32AWG Ni200 and stuffing just 5 wraps in.
Be forewarned, while I don't know if my center pin is out of spec or not, the screw on the center pin which clamps on the wire won't clamp onto even 28AWG let alone anything smaller gauge.
Presently I have a Chinese NI200 coil installed in mine - seems to be working ok, no leaks yet!
Edit: I just tried making a vertical coil. I used the: insert coil and stuff the cotton in later method with some success. Next I may line the inside of the RA with cotton and insert the coil. Oddly my 1st attempt had less air flow than the horizontal coil I built earlier. Much easier to ensure that the center pin is not shorting out to the outside. I'll have to try another one later.