I ran a 7' one behind my
L3200, 32hp, 2,500lbs orvso. Had to go slow, but it did decent.
I paid $100 for the beat to hell flail 8-9 years ago. Have maybe $500 into it now with a PTO shaft, belts, new knives & some bearings. It's survived 5+ years as my main mower for my side hustle. My new flail is currently down due to roller bearings. So I've been using the Ford this year & haven't gotten to fixing my main Peruzzo. It's still beat to hell with a cracked hood & lots of other issues. But it's still working at probably 20+ years old.