Thought I'd chime in with my experiences on the pads as well. I use the C2 pads paired with the AP Racing Sprint kit on the front and C1 pads on the OEM rears for my 14 BRZ.
I came from the PMU Racing999s and think that the CSG pads are much more predictable and linear in pedal feel. The initial bite felt great and inspires confidence. I used them with both 245/40R17 GT Radial Champiro SX2 on 17x9.5 TE37SL as well as 225/45R17 RE-71Rs on 17x7.5 Enkei RPF1s.
I had a coach with me at Autobahn Country Club in Joliet and we were doing back to back sessions (8 30 minute sessions in total each day for two days) with zero fade or surprises from the brakes. He drives Porsches and Radicals at the track and said the pads were similar in feel and predictability to the Pagids on his Boxster.
I can't speak to longevity because I managed to get one of the AP Racing calipers stuck out and dragging on the pad, but it didn't have bad wear with what we put them through for those sessions.
The only real downside I've noticed is that they are loud AF on the street. Coming from the relatively quieter PMU Racing999s, it definitely embarrassed my passengers lol. But I switch back to G-Loc GS1s after the season is over so it's not horrible.
We did set NA BRZ track records at Autobahn South on those days even with my shot suspension, so there's that
