I have Ags on my B7300 I was looking to replace with R4's. I have the same fronts your tractor takes, 6-12's...but my rears are 8.3-16's rather than 9.5-16's specified for your tractor. You'd still be within the ratio percentage I believe but could be something you should verify. There are 150 hours on these tires, always stored in doors. Would you want a rear that is 1" narrower. Then of course we have distance from each other to contend with.
KP