on 28ga @ 1/16" ID, aprox 10 wraps will bring you to approx 1 ohm so dual 10 wraps will be only .5 ohm... point being that to do 28ga and not go really low sub ohms you'll need to do long coils like I have shown... 20 wraps each coil at ~1/16th inner dia. will net around 2 ohms each, duals in this config will be around 1 ohm... I'd probably shoot for between 18-20 wraps each... the heat up time on something like this may be a several seconds though whenever you hit it from cold... def doable with 28ga but I find 30 to be better for this particular build, just heats up a bit faster, my dual 13 wrap 30ga heats up in a second or 2 but duals @28ga certainly isn't bad and will work but you really need to use a meter or something because 28ga duals are really easy to go too low with, I wouldn't go lower than .8-.9 or so, even if your mech can handle the power the kayfun won't be able to keep up with wicking at these power levels, especially with duals... you should pick up some 30 ga to play with these ideally