Yea - putting a heatsink on the bottom of the spee controller will help - you need a compound to effectively transfer the heat from the speed controller to your heatsink - an efficient transfer of heat will reduce the temps substantially - i went from thermaling after 6 mins being easy on the throttle to 35 mins and hammering the snot out of the throttle trying to thermal her.... Good luck.... btw - check out this stuff called artic silver - works awesome

And to add to HNC's reply: If you want to bond the heatsink to the ESC case, use thermal adhesive, not simply thermal compound. The link for the Arctive Silver adhesive is: http://www.arcticsilver.com/arctic_s...l_adhesive.htm

Be warned, it is considered permanent. If you use normal thermal compound, you'll have to find a way to hold the two parts firmly together and not move around (hard to do win an r/c car).