I would definitely go with a 4-footer. I have a five-footer on my S470d Buck (It's just a little bit bigger, little more HP than a Beaver), and it's just too much for that tractor. Part of that is this mower's weight....it's very, very heavy, and does not have front guide wheels, so the front of the mower hangs on the back of the tractor with check chains. It's possible that you could run a 5-footer that has four guide wheels, but that's still a lot of mower for your tractor. The footprint on the 5-foot mower is much larger than the tire track, so I wind up mowing over stuff I've already mowed, anyway. The mower was bought with the tractor some 30 years ago, and came with it when I bought them a couple years ago. I would've matched it with a 4-footer Woods finish mower or something like that.