I'm pretty happy with my new heatsink so I thought I'd share. It's a Quark 80b esc and the heatsink is machined so that it fits into a cut-out in the bottom of the Quark case (inverted) and is in direct contact with the fets through transfer paste. I then epoxied the bottom of the heatsink to the case for strength and then tied the whole thing together and into the buggy with steel wire.
I've been getting 15 minutes of hard running before the esc gets hot and I still had lots of battery left. Now I can run 25+ min to the lvc and it only gets warm. Seems to run a little smoother too, especially when it's warm.
Now I'm ready for the track!