I run a 7' "rotary cutter" , but not a Bush Hog brand. It's a Frontier RC2084 sold by John Deere.
I run it on a ~65Hp (PTO) tractor. Tractor only feels it there if mowing tall grass, or when raised on 3pth.
About a 1000lbs. It feels heavy on the back, you want some front
ballast or a FEL on, but it's still built too light....or maybe its me.
About 1/3 of the time I use it I'm bending the sidewalls into the blades. Makes a h*ll of a noise. Then I have to get chains and a come-along and 2 good anchor points to try and bend them back away.
Sometime it's my fault when I back into the "unknown" and run into a stump, rock, fence post etc... I wish there was a more heavy duty, squared off bumper. I've gotten better at not doing that.
Now they get bent in from turning on uneven ground without lifting it enough. It's easy to find "uneven ground" when it's 7' wide.
Bumping into a couple 6" tall pine stumps has ripped off both the front and back chain guard bars.
After 7 years I have a front bearing seal starting to leak. Probably the vent/fill plug failed. I haven't replaced the seal yet, just topped the oil off, but will replace it this spring.
If I had to do it over, I would of got a 6' as I tend to mostly mow around odd spots instead of fields and pastures. 7' foot can cover some ground, but not as maneuverable.
Don't worry about having width that matches tractor width unless you're trying to get next to fences and buildings.