To settle this:
Yes, it's a WELL known fact that the suby 4 pots fit under the GC chassis RS wheels. The ones that are 16x7. I've got a set that are shod with my race rubber.
To answer the original question, I can only answer from the perspective of the Suby 4 pots. Mine have been thru 3 track days and have held up extremely well lap after lap. Even at Roebling Road, where the end of the front straight I was seeing 120+
The brakes never even hinted at fade after 12-15 minute sessions.
For a bit of empirical data, all HPDEs have been run with Porterfield R4S pads.