When choosing a boxblade, do you try to buy one that is wider than your rear footprint? I don't want overburden the tractor, but I also don't want to buy to small. It will be used on a B7500 Kubota.
JD 8320 MFWD, JD 6415 MFWD, FEL, and cab, John Deere MFWD 4600, John Deere 4020, John Deere 4430, John Deere 455 mower, Deutz, and Gehl 4610 perkins skidsteer
Yes you try to get one that will cover your rear tracks so you don't have to go back over the area that you did or leave tracks, etc. where you ahve already been.
Go with the width. A couple of dealers thought I could go up to a 54" or 60" blade with the B7500, but in the end I ended up with a 48" Woods. This puppy is very heavy, closely matches the width of the tractor, and stays within your traction limitations.
Like the other guys said, you definitely want one wider than the outside of your rear tread. My B7100 was 40", so I used a 4' box blade. My B2710 is 54" so I'm using a 5' box blade.