Folks - a well timed thread.
I installed PFC-01 pads in OEM calipers and used them on Friday for the first time. I found that the pads rattle in the calipers when hot and just rolling/taxiing slowly. The noise went when the brakes were applied. Is this usual? Initially it was the passenger side front only, and then it was both sides after a more vigorous session. The PFC pads do not have retaining springs.
The brakes worked fine, but the rattle was disconcerting and drew some attention in the paddock coming in off the track. The rattling went away when the pads were cool.