Cruiser97_80
Rx8 5000 series are still not available. Grrr

They not going to be made available.  Just went through this, Directly from DBA, "there are none and we are not interested in making them"
 
I currently have RDA RX8 rotors on my car, My car isn't registered and it used for sprint racing, we get 4 laps for 5 rounds, a lap is about 45seconds.
After looking at the RX8 rotors and the fact my car is well over braked, I put the rotors in my brake lathe and removed as much of the redundant metal as I felt I could. 
There was 2mm of excess diameter, I took them down to 22.1mm (22mm in min thickness).
Using a boring bar normally used for drums I removed excess metal at the ID of the inside friction surface.
then tapered that back to the just outside the pad area.
I had the car rolling in hurry as I needed the hoist space for customer jobs, so they haven't be put on a scale.  
As best I have is a quote from a friend who was skeptical about it.   He held them and said "well, you can feel a difference".
In all honesty I be surprised if it was worth more then 1kg per rotor.
How ever, at our last round, there was 0.09second between 1st and 3rd and only 0.03 back to 4th.
So for me any gain could be the difference.
I'm yet to do the front rotors, but they will get the machined with the same principles.
You can see the photos on my facebook page.  Edit, seems the forum doesn't allow FB links.