Most guys try to run 2-offs all the way around, in order to get the widest wheelbase footprint legally possible.
However, on very hard dry slick tracks, if you run a 3-off or a 4-off on the right rear only, with 2-offs on the other three, you will get more roll center "sidebite" traction stability in and out of the corners.
On wet heavy tracks, run a 2-off on the right rear also.
Use a good beadlock on right rear either way if your rules will allow.