How do you know if theyre set inwards or wide? Mine are about 65" from edge to edge in the rear of my 4720 with R4s... can they move out wider? My smallest bucket is a 72" so another few inches either side wont hurt.
I have seen some models of the 4x20 series tractors with the multi-position rims and R4 tires. With those rims you (theoretically, at least) could have the wheels in 8 different positions.
Your owner's manual should refer to the various positions that the rims can be used. If you have the 2-position rims with R4's (like me) it's pretty straight-forward.
If you have the regular R4 wheels and only have in or out. The widest position will be with the air valves turned in. The width gain is minimal at best, but I guess something is better than nothing.