You need to use 30 or 32 gauge . 28 ga would require a lot of wire, thus heating slow. To use with your ProVari, and just for plain safety, stay above 1.2 ohms. If you can't get the dual coil build down, building two at a time, try dropping back to one coil. Get your coil built. Measure the resistance then divide by 2. That will give you the approximate resistance of a dual coil build , built with two coils identical to the one you just built. So if you built a coil using 32 g at 12 wraps and it measures 3 ohms, divide by 2 and you get 1.5 ohms. That's what the resistance would be if you used the same coil in a dual coil build.