What do you mean by "Be very careful about setting those pots to "a lot more" than 100ma,
that's a good way to make the IRF510's pop from the heat." What's a lot more? I found I needed to adjust my bias to 150mA each just to get the PO to be on par with most others. By your formula above I would get 12v*0.150A=1.8 watt. Am I correct?
Do you - or anyone here - have suggested maximum bias mA's? (BTW, I have a rather large computer cabinet fan that I salvaged and blow directly on the PAs.}