I found that even with my older SPF, factory/stock pads just won't cut it for any kind of spirited driving; let alone track work. Dennis Olthoff set me up with better metallic/carbon pads that are a bit harsher on the discs but will stop the car. Also, for anything over a lap, you'd need to change the brake fluid to SRF or similar higher boiling point
synthetic brake fluid, and of course, s/s braided lines. Your problem may be a combination of the above shortcomings. The 70-0 you speak about, was that after many runs or from cold?
Please keep us posted as this is bad news and I hope your issues get resolved.