That 525 probably had 108 rails...
Lee, I think you had one with the hottest transformer. How hot was THAT one?
Also, clipping is subjective. Most people cannot detect a good percentage of clipping distortion at high Sound Pressure Levels, even though it is obvious on a scope. I believe the RMS voltage does go up a little bit during clipping, therefore the Power in Watts continues to increase.
From Wikipedia:
"Amplifiers have voltage, current and thermal limits. Clipping may occur due to limitations in the power supply or the output stage. Some amplifiers are able to deliver peak power without clipping for short durations before energy stored in the power supply is depleted or the amplifier begins to overheat."
And...
"Because the clipped waveform has more area underneath it than the smaller unclipped waveform, the amplifier produces more power than its rated sine wave output when it is clipping."