There is now an aftermarket ALLUMINUM (LIGHTWEIGHT) option available. Its a bit pricey at 658 a housing. But They have alluminum rotor housings and front, intermediate, and rear housing for the 13b. I guess i was super tired when i came across it cuz after looking at it again it makes total sense. I was looking at rebuild options for something i might be toying around with shortly. But with more than 3 grand just in housing.... it might be a slow process (i havent even looked at the light rotors yet). They make S4 and S5 housing which is why i was curious as to which housing would provide better performance opportunities. Also, the alluminum claims better wear and longevity than the origianl housing found on the stock 13b's.