Looking at the Bush Hog Squealer brochure; (newer slopeback models) the 4' is listed @ 455lbs, and the 5' is showing 636lbs so that particular model has a large jump in weight. I presume these weights are as "standard equipment" with non laminated tailwheel, and the front rubber strip and rear bolt on band, which some dealers delete when the units are ordered. The 5' does step up to a 65hp gearbox, but has the same gauge steel. The Razorback model in the 5' size weighs 450lbs with lighter 11ga steel deck and sides, uses a 40hp gearbox, and 3/8 x3 blades versus the Squealers 1/2 x 4. Extra HP is always nice with a larger cutter, but I think a lot of manufacturers rate the cutters as they do partially to prevent folks from overloading the tractor weightwise and having an accident from the tail wagging the dog syndrome. As said above, just take a smaller bite, or just drive the tractor slower at a high PTO speed, and if it takes a little longer in the tall stuff, so be it. I would order/buy the cutter with a slip clutch vs the shearbolt, and set the clutch a little looser than as shipped the help protect the tractor driveline. A friend of mine was teaching his 15yo son to use cutter, and had been doing good for a while, but for some reason he started tractor up after a water break, set PRM's at max (??) in neutral, engaged PTO, and at the same time let his wet boot slip off the clutch. Someone had replaced the soft grade 2 shearbolt with a grade 5 and it broke the yoke, but it could have been the tractor. For that reason I would not ever consider another cutter without a slip clutch, especially on one where the cutter may be on the large side. I don't think you will have any problem with the larger cutters, just don't over do it, good luck.
