Ditto on 85Hokies experience above. Also have a 5' hog behind my Ford 4000 with live PTO...have cut 2-2 1/2" diameter trees, smaller ones by driving over and larger ones by backing up and letting the hog slowly naw at them. The used 5 footer hog from an earlier era that I bought, while I don't think Ford made it, had their logo on it.. extremely heavy built unit and has it's own adjustable torque limiting clutch.. when it's on the back of a 4000 lb tractor, easy to do wheelies when going up through the gears on the road, needs the 52 hp my Ford has to run it.
The brush pictured by the OP would be a piece of cake with a bush hog.. Cleared my forrested land driveway path and house site using one, plus chainsaw for the big stuff..
Got to be careful driving over stuff... if you try to do that over stuff too big for your tractor to make it all the way over for the bush hog to chew up, you can get stuck.. When you try to back up, it bows up even stronger saying to your tractor I got you SOB!
Also good to have a well adjusted slip clutch on the bush hog. That kind of shock loading can be hard on the drive train. Even though I have a live PTO, I put a PTO overrun adapter on as the inertial loading of that much rotating mass in the larger, heavy duty bush hogs feeds back into the drivetrain every time you move the throttle.
Not a problem with modern tractors like the Kubota, but as most probably already know, ground speed PTOs on found on old generation tractors driving a bush hog without an overrun clutch are killers especially around ditches...
I know, I know... "bush hog" is a brand name but "brush cutter" sounds so tame after you lived with one. Heavy boots are good to have on while on the tractor... they can throw considerable sized chunks forward toward your feet..