78amps is the maximum continous rating of the motor, but it will pull larger peaks than that, up around 120-150 quite easily.
I wouldnt use anything less 3500-4000mah personally, regardless of the C rating- a total of 4s lipo will still only weigh roughly the same as a single 6/7 cell nimh pack, so weight shouldnt be an issue.
1. possibly. Even with a high C rating, the lower mah capacity limits the maximum amount of current the lipo can discharge; 106amps is borderline at best, upwards of 120 would be more ideal.
2. A ten minute race isnt all that long I guess, and people say a ~5000mah pack can last 20-25 minutes under racing conditions. If you know how many mah you are using with your other larger lipos, then you can calculate how many you need + a little overhead and base your next lightweight setup on that.
Thats my thinking anyway, but see what the racers around here have to say
