Hi everyone, thanks for the feedback.
The transformer output spec is 24v RMS which should make almost 34v peak. I measured the output of the 40000uF caps, and they were 30.4v (with a very small load, and thus very little ripple). So yes, you might be correct that regulation will not work properly at 60v (or 30v depending on the mode). Maybe I can change the spec to 25v or 50v max (and add a series resistor between the voltage regulation pot and the 5v reference to limit the max voltage).
Concerning total power dissipation, each output transistor has its own heat sink measuring 5"x4"x1.5", and the chassis has a fan in the back. That said, I just completed the construction and have not done much testing to see if the airflow is sufficient. I have run it in the 30v mode with the outputs shorted and the current limit set to 20amps for 1 minute, and could still hold my fingers to the heatsinks, but they were still getting hotter (not a good sign). The design should work so long as the output transistors stay below 80 deg c. (Each MJ15024 is rated for 250wats, which derate at 1.43w/deg.c above 25deg.c, which is still 171 wats each)
I don't understand the comment about needing 0.1F caps for smoothing. The circuit has a feedback loop to control the pass transistor, which will regulate the output voltage. The voltage at the output of the 40000uF caps can ripple, that's ok.
I also don't understand why the transformer is unsafe. What does earthbounded mean, and what needs to be double insulated?
Thanks for pointing out the current measuring shunt being outside the voltage measurement loop. I can move the bottom of R6 to the -output to correct this.
Again, thanks for all the comments.
-Paul