Piston sizes are not identical.
17z's actually have larger piston diameters.
New Progressive upgrade calipers should work with these rotors.
http://forums.racingbrake.com/showthread.php?t=849
Yes you can fit the new RB460 caliper with OEM R32 345x30 rotors or RB's Two-Piece 345x30 rotors.
These Cayenne rotors with the appropriate adapter should work with the RB460's.
The RB460's are going through R&D still and should be run at the track in the coming weeks before being released.
Keep in mind that you will need 18" wheels to fit the RB460 calipers.
I know how you feel PandaGti I want these for my MK4R32 as well. :thumbup:
That's exciting... As soon as these rotor rings wear out I can upgrade to bigger ones