Dennis, I would decrease the air pressure in the tag airbags down to 0 (we have a adjustable regulator) and doubt we would have to do anything else with one tire off the rim other than to air up the drive axle tires to max cold pressure and keep the speed down.
I currently have 315's on the front and 11R22.5 on all six rear tires and I carry a 295 unmounted spare tire. When I had 295's all the way around I carried a 275 spare tire (had a good one that size) and if a 295 was not available the 275 would go on the tag and the 295 where it was needed.