Hey man I have RCX 5" with with 20x10 -12 fuel mavs, running 305/55/20 nitto trails. No rubbing or issues with them at all. I recently installed the TGC .5" front lower strut spacer to make it sit totally level. I am also wondering the same thing about tire size at this point, what I have looks fine but would like to have larger tread if possible but have not seen anything out there.
hope this helps.