Hung out the afternoon at the local B&M. It's family owned and operated by some truly nice human beings. The 19 yo son makes all of Kidney Punchers premade coils. His work is artful... Rebuilt two GS TC heads while I was there. Should have taken some pics but I didn't. Both were horizontal builds, 7/8 wraps @ 2.5mm ⌀, spaced. Seems to be a good size for performance and wicking with rayon. The first was 26g NiCr60 @ .70Ω (barely spaced). The second was with 28g SS316L @ .74Ω (.5mm(ish) spacing). I have to say they vaped pretty great in one of the new GS Airs. The NiCr peaked, in VW mode, around 35-40W. The SS was awesome in TC @ 420-460F & 25W and 30W in VW mode.. From watching Cheech's videos, the TC coils may be a bit easier to rebuild, after you get them apart! I figured out how to do that fairly simply after the first TOTAL FAIL. Wicking couldn't be easier, trimmed a hair beyond the head casing. Everyone said they outperformed the stock heads, which I didn't get the chance to try. The GS Air tank really is fine. I just hate the stupid sillycone vape band/AFC.
ETA: I realized after posting that my story was not very helpful to most in this thread. I would suggest most rebuild these, for non-TC use, at 2.5mm ⌀ with KanthalA1, 28g, 6/7 wrap, spaced @ 1.25Ω. This build is great from 12W-25W in the GS Air. At 10W, this will provide a very cool vape.
If you are a true tootle puffer, but like some warmth, 6/7 wraps of 30g, @ 1.9Ω, will perform great from 7-15W... If you wanted, you could go with 30g Nichrome60 (NiCr60) and total 1.5Ω. This is probably closest to a stock horizontal GS coil. But it would surely outshine said stock coil.
Wick both fairly chunky with rayon, trim to just beyond head casing and I think you'd be very happy.