It's time to replace my rear brakes and I'm curious about a possible upgrade... has anyone ever tried fitting the rear brakes from the e34 540/M5 on their 850? The rears are a bit larger (300 mm x 20 mm) and vented instead of the 8's solid rears. I have the disks and they do fit, yet not with the existing caliper. The real question is if the e34 caliper would attach to the 850 mounting points?