well my hcigar vt200 shorted with a brass bolt I had a mod resistance of .005 so I put it as .0045 so its 90%. seems like the brass 510 really helps cut down the resistnce.
what ive been doing for dual coils is working pretty good. i cut two wires exactly the same length and wrap my coil and install without cutting any of the wire. I use steam engine to find out the exact length needed for my build.
My vt200 last all day at 60w 100w preheat. II vape about 25mls out of a aromamizer rdta. It took a few full discharge cycles till I noticed longer battery life.