Quark 125B works, but stops after 3 minutes...

[BrianG]

The internal mod may or may not be needed. It depends on how long the thermal pad holds up. After a while the adhesive bond weakena and the ESC will seperate from the case. When that happens, the FETs aren't contacting anything so they overheat MUCH quicker.

Some of those thermal pads hold up ok for longer time than others. So, just because some people still have no heat issues doesn't necessarily mean you won't.

One way to tell if temps are the issue is to feel the ESC case and then the PCB at the motor wires. If the case is cool or just warm, but the wires are hot, then the FETs aren't making good contact. I've modded both my Quarks and have yet to have any trouble with heat.