yellowducman

Aren't the holes in factory Porsche rotor (the ones with holes) cast in, not drilled in? I always thought that it was where the metal was stressed around the hole when drilled that caused it to crack. I've always heard that slotted rotors are good though because the machine doesn't cause the machining doesn't cause the stressing to the metal and it gives the gasses between the pad and the rotor somewhere to go. Of course this is only applies to cars driven hard on the track. I have had cracks appear between the slots and the ends of the rotor on my Subaru STI after a couple of track days though.

Gasser

I have heard that but not sure where the truth lies. I can tell you though, I use stock 993 rotors that have the holes and I have put them through HELL as our local short track is hard on brakes and NO cracks. They hold up very well. I don't have any options for solid rotors as they don't make them for the 993 but If I did, I would switch to solid rotors with slots jusf for the added mass.
That said, I do have very good brake cooling ducts so that may explain why mine last so well.

FWIW

Jeff