Chris,
No time right now to write the article .. 2 kids are keeping me busy
The original 'Hats' that come on the 993TT rotors give the wheels more less offset (5mm) than the ones I had machined .. sold those for what I paid for them. I needed the offset decrease so my wheels would not rub on the lower trailing arm at full lock.
You can use the original rotors but fit everything before you see a machinist !
Sandeep