I was working on a project to run the 993 TT rotor and the 996/boxter S monobloc caliper. I abonded the project along with a few other things on my car, but that is beside the point. There is enough room to run the rotor and caliper on the Z spindle. The hat I used to test fit was from a friend's Pcar kit for his audi. here are all the pics I took. I was planning on running the z31 5 lug hubs. I have a feeling with the hat ive got, and standard hubs, things would get close.
The rotors are 322x28 IIRC. This set of calipers has to have the pad centering pins clearanced 1mm on each side to clear the rotor. It doesnt hurt the caliper at all. This setup was going to fit barely behind starion 16" wheels.
This type of kit is very popular among the VW/Audi crowd. Rotors are $215 each on the net, and the pair of calipers usually sell for around $400.
Anyways, I hope that info helps someone along the way