I'm running dual coils in the Nipple on the mech T-mod. It's a 22mm atty, but because of the post orientation and the domed top cap, it's a pretty tight fit (because I refuse to do vertical coils). If I remember correctly, I do 2.5mm in that one, but I'll double check it here shortly.
It's hard for me to manipulate everything with my funky hands. I have to wrap on a coiler, I take that out, & put a longer mandrel in, & use that for the install. The coiler gives me slightly spaced coils with the SS, a little bigger than 2.5. I could use a pait of needlenose pliers & pull it tighter on the mandrel, but that ends up lower than I want to be. 1.1 is almost too low. 1.3 - 1.5 is my happy place with my juices & flavor in my KF's & RM2.
I can completely understand that. That little bit of slack in the wraps can make the bit of difference that you need to keep your res where you want it. I tend to go low with most of my builds, so keeping them tight is the only way that I can stay consistent. Believe it or not, even 0.25Ω often doesn't give me a warm enough vape unless I close up the air flow a bit. That's one of the reasons that I've gone up to 3mm coils when the atty allows for it... bigger coils seem to be easier for me to control. But that could all just be in my head.

For kanthal only, torching it first takes out most of the spring. And a regular butane lighter is good enough![]()
I haven't found that annealing SS makes much difference for me... definitely did with kanthal, though.