Sometimes I feel that after some heavy brakings with 3 digit speeds the rear just isn't as it was before, seems to let go a bit and also I 've noticed that rear disks and pads are wearing a bit more rappidlly than the front ones so that tells me that they are overworking... (AP330mm with 4pot calipers on the front by the way). I have found somewhere 4pot calipers with mechanical handbrake mechanism but I don't remember the brand now...