We run both 5-ft and 6-ft rotary cutters aka brush-hog or bush-hog.
Slip clutch or shear pin is personal preference. Clutch requires occasional adjustment to work correctly and springs can weaken over time with use. If shear pin use ONLY 'no-grade' (no marks on bolt head) Grade-2 bolts and either use jam-nut or NyLock nuts. Get a bolt of enough length to make the nut tight to the shank with no threads inside the U-joint body. Cut off excess for safety (snagging shirt sleeves, wad of grass catching fire from friction).
I think the one-lenth-fits-all pins that have ten cotter key holes in them are too weak and shear too easily. Keep spare pins on hand. You can buy shear pins of correct length with one cotter key hole but bolts are cheaper. Grease pin when installing will come out easier. You'll need a drift to get the broken pin out. Stay away from pound-in type swedged, splined, or 'watermelon' pins as are PiA to get out when broken. Use a center-punch or small chisel to mark U-joint and gearbox shaft after installing pin to indicate when holes are lined up. I sometimes have trouble seeing through the U-joint yoke to where the sheared pin is smeared across the hole.
Stump jumper is round tub-looking thing under deck to which blades are mounted and in theory rides up and over stumps and rocks. Straight blade bar will get you in trouble if it wraps around a stump or other obstruction and can set the entire machine sideways faster than you can think.
In any case make certain there is an access port on top deck to reach nut on special blade-mounting bolt. Or cut hole in deck with torch to reach nut. You'll have absolute heck trying to get the stump-jumper off the gearbox shaft if that's the intended way to change blades.
You may need to get a bushhog wrench (socket on a big square stick; use a BIG cresent or pipe wrench) if you don't have a 3/4-in drive ratchet set. Or check pawn shop tool bins for correct socket and extension and break-over (expect to use a cheater pipe). Clean bolt keyway and lube threads when reinstalling.
Sharper blades cut better and faster and require less horsepower. Something like a dull dinner knife, not a razor edge. Sharpen blades off the machine with a 4.5-in handgrinder.
Keep U-joints greased and check gearbox (use 85-140-wt gear oil) or as specified by mfgr.
When reinstalling blades when buying replacements be sure you get the correct blades (hundreds to choose from) and orient them correctly for upside-down and direction of rotation. Best to mark old blades BOTTOM before removing.
Blades can, do, and will bend and break. Change when necessary or if bad chips/cracks evident (inspect regularly if anything more than golf-course grass cutting). If blade breaks turn the PTO off immediately (you'll know from violent vibration and first time it happens the immediate need to hose off tractor seat).
Be careful, stay thoughtful, and learn the machine.
Please keep us posted as your next adventure in equipment unfolds.
