285/30/20 is a common application and it is available in PSS. Only problem is the matching size for the front which would be 255/30/20 is not available in PSS. There is a 245/30/20 available if you're comfortable running a tire with a load rating that much lower than OEM. I decided not to go in that direction and instead got PS2s in 255/30/20 and 305/25/20.
FYI, I used to have Vreds in 255/30/20 and 285/30/20 with no fitment issues. I wouldn't run 285/25/20. Load rating is way too low and significantly smaller in diameter than OEM.
2016 Porsche Cayman GTS - Sapphire Blue / Black Full Leather Interior / Carrera S Wheels