The vertical build would SO be a huge help to me right now. I have KFs and use cellucotton. I have had 4 surgeries in two months to try and build an access for hemodialysis. The last one almost resulted in almost losing most of the fine motor skill usage of my right arm so I am recuperating from that and placing a horizontal coil is a real PIA. I'm trying to catch up on the technique but my somewhat addled brain (way too much anesthesia for a person of my age in a 6 hour time slot) is not putting it all together. I've been making my own coils for about 8 months and placing them is never easy but is quite a challenge right now. It will get better but the vertical technique looks to be somewhat less taxing than the horizontal. Can you possibly encapsulate your knowledge and technique especially about how you wick and where you terminate the wick ends around the juice channels.
Oh my. I'll try. Disclaimer: I only used vertical coils w/ hemp for wicking for about a month. Then when I stopped using hemp - I went back to horizontil coils.
You don't really get to choose the diameter of your coil. The size of the air hole pretty much determines the coil size. Find something that fits into the air hole, a screw driver, drill bit, skewer, toothpick, whatever. Use that to wrap your coil. After wrapping the coil I'd take it off the 'mandrel' and hold it in the jaws of a pair of forceps and hit it with the torch to 'set it' (to hold the coil wraps close to each other). I found it tricky to do this once installed on the PV and using the PV to 'glow' the coil then squeeze it together w/ tweezers. (Which is what I do w/ horizontal coils)
The with the coil on the 'mandrel' put it into the air hole and connect the + and - posts. I'd attach the positive lead 1st. The adjust the height of the coil over the air hole (a couple-few millimeters). Then holding the 'mandrel' verticle carefully bend the negative lead (which will be on top of the coil) down and the around the negative screw. This is probably the trickiest part.
When I wicked w/ hemp, I'd cut the hemp up into small pieces and soak it in vg. Then take small clumps of the soaked/hemp and start packing it loosely into the chamber until the entire chamber was filled to the height of the top of the coil. It took a couple attempts to get the feel for 'how loose' / 'how tight' to pack the hemp. Too loose and I'd get flooding, too tight and it wouldn't wick well (yuck - dry hits).
If I were doing it with cotton. I'd probably pack the cotton dry about 1/2 way 'up'. Then wet it down and wait a minute or 2 to let it soak up the liquid, then repeat 'till I got to the height of the top of the coil.
That's 'bout it for what I can think to say. If you try it and have issues or more questions. Just post away here, what you tried and what didn't work and I'll gladly try to help you.
Also - you can go here and see what folks better then me have to say about vertical coils.
http://www.e-cigarette-forum.com/forum/rebuildable-atomizer-systems/481316-vcore-vertical-micro-coil-oddy-kayfun-russian-ithaca-ect.html