Oh man, your using spacers on the screw between the Mosfet block and the motherboard aren't you? spaced just long enough where the block gets just the right amount of pressure on the Mosfets with the thermal pad, but still gets a fully tightened down mount on the motherboard.

Thats genius, I mean i assume thats what your doing, you mentioned small parts being able to solve the problem of having either a semi loose mount or a bowed mount, thats got to be it, thats seriously awesome.