mamba 25 done. Did a 5s test with lower gearing, and freshly charged batts. Cogging not much of an issue with lower gearing, couple other quick checks ok, and staight to the hill for part throttle testing. I had already performed same test repeatedly with half charged 5s and much taller gearing. This time I expected temps to drop (lower gearing), I didn't even start up the hill and puff. It seems the fresh pack put voltage a little to high.

After this I got to talk to a very knowledgeable brushless airplane guy. Here are a few thoughts he had-
#1 - at full throttle fets don't work nearly as hard as at part throttle (what I saw in testing proved this even @ lower voltages, but went critical on higher)
#2 - out-runners are not the best motors to try to over power; they suffer iron saturation and act almost like a dead short when overloaded
#3 - cheap batts cause ripple currents ( a little spike getting through the cap would easily kill the fets., but the higher nominal voltage good batts would provide would not be good either on 5s)

So. if I want to continue I need to go with a top notch motor (Neu or mega), best quality 4s pack, and gear to use full throttle as much as possible