A buddy of mine hauled his stock M146 (9.00x20 tires) behind his M931A2. The rear tires on the tractor would sometimes catch on the trailer landing gear feet, so he trimmed the inside corners of the pads. Still a bit too close for my taste though (and his. He hauls it with his M915 now).
11.00x20's would probably fit that trailer without modification, and that would lift the back end up a bit, and make it look better back there. Somebody who has tried it needs to chime in on that though.
One of my M931A2's has been retrofitted with a civilian Fontaine slider 5th wheel. It lowers the plate height by slightly over 6" from the military double-tilt 5th wheel, which I didn't need. This in turn lowers the top of the trailer nose by a like amount, changes the angle of the trailer a bit, and you can slide it back some for short-necked trailers like an M146.
The M129 would make a great camper, but it is a lot of trailer! It comes stock with 11.00s.
Cheers
Pic 1- M931A2 with stock M146
Pic 2- My M931A2 with M129A4 (standard military 5th wheel, not the Fontaine). It measures 13'9" at the nose of the trailer (!)