I could be wrong but my understanding has always been that the C rating is how much current you can pull out of it which is the same as saying how fast you can discharge it safely. example: 1000 mah batt. 7C would mean you should never exceed 7x1000ma (7 amps) during discharge. An electric motor does not pull current at a linear rate in all flying conditions. So, if we have a motor that draws 3 amps at a steady state hover then I would guess that it could probably pull 6-7 amps in a stress condition of accelerating hard. So, I would be much more comfortable with a 12C batt. in my Emaxx RC truck I use extremely high performance sub-C cells that can easily handle 30 amps and cost way more than a standard pack of C size rechargables from Radio Shack. Cost is very much related to the ability of a cell to handle current.