[Serum]

That white stuff doesn't isolate. The top of the case of most SMD fetts are isolated allready.

A past normally doesn't isolate (elctrical), that's what the silicone or mylar isolators are for. With normal transistors, the metal part of the housing is normally electrical connected and needs to be isolated from eachoters in some designs.

Are you going to have those heatsinks machined? feel free to make a 2nd one for me.. :p