I have a Sigelei 100+ mod with two VTC4 batts in it. My current build is .15ohm. Looking at steam engine that should be fine as I have a 20% headroom, but since my mod is dual batts, that is actually 40% headroom right? I have read ohms law, and every other sticky I can find on multiple forums, and I think I know what Im doing. I do know that even when I ran it at 90watts the batts never got warm, but then I started thinking... Just wanted to check with smarter people than I on this. I normally build at .25 to .5, but I was playing with 24g Parallel build and ended up with a .15ohm dual coil set up. I have never been able to comfortably run higher than 60w with my normal builds but this thing is sweet all the way up. yes I know Im really representing my user name by asking this, but I just dont wanna end up with a hand full of F**k here.