Hi Dave, yep its 10:30 at night, and getting ready to hit the hay
I dont think my esc's get over 10deg above ambient in normal operation, but the are 25 amp rated, and only operate at about 5 amps in hovering.
Would I fit heat sinks ? if my temps were getting over 40-50 deg , yes, as with Mosfets its a vicious cycle, heat causes higher resistance in the mosfet, which causes more heat, and so on. (Mosfets are the semiconductor switches used in BL's)
I would change the mounting to get the heat sink fins vertical, and would also try (where possible) to make sure the heat from the ESC's was away from the controller (radiated heat affecting gyros)
On my quad, the ESC's are mounted on the ally arms, which seem to do a good job conducting the heat away
My New Quad design, i have the ESC's mounted at the very top, with the rest of the electrics slung underneath, will post up some photos when the parts get back from the waterjet cutter