MAH wont cause any more heat, other than letting it run longer, that big battery wont turn your motor any faster than the small one, the big battery just stores more of the 7.2 volt power, if your getting too hot now, you should cut some holes in the body to get some air to the esc, i ran the traxxas 380 motor/esc in my mini 8ight on 3s lipo,and didnt have any heating problems, the losi setups run on the warm side anyway, what are your temps after about 6 or 7 minutes of runtime?