Hey

What do you think of a design like this one? An aluminium chassis (2mm thick Al sheet) with sides bent to 6 cm
The power board with it's transistors attached to the chassis, and the back side of the chassis with riveted fins
made of an U shapes structural Al bar.

This design may be useful? Or are the fins useless because of the poor thermal contact with the rest of the chassis?
I've seen this kind of heatsinks used in 7.1 surround sound equipment, (aluminium plate with riveted fins, but the PA
for this equipment is a class H chipamp that should run very cool all the time, or most of the time.