I have the 6' caroni and I used it for the first time this year at our hunting lease to mow down food plots and logging roads. For 1 to 2 ft grass, I can pull it at about 3 to 3 1/2 mph. For 5 to 6' weeds, stuff higher than the tractor, I am reduced to a crawl and burned up 3 sets of belts (at about $40/set). This high stuff completely fills the flail housing and it can't spit it out fast enough. The result is burning your belts. My partner was pulling his 8 ft rotary at 6 mph over the same stuff including the 5 to 6' high weeds, but he has 40 more hp than me.
My flail won't cut saplings much bigger than your index finger. It will strip it and lay it down, but not cut it.
Lesson here: If you are going to be cutting really thick tall stuff, go w/ the rotary.
The flail projects about 4' behind my tractor vs. over 10' for a rotary of the same size. It fits nicely on my trailer and is great in tight places on small plots or in the woods. This is really a huge, huge plus. With a rotary, I get neck strain always making sure I'm not going to swing it against a tree, bldg, or other equipment. I can't begin to load my tractor w/ a rotary on my trailer w/o 3' hanging off the back which I think is frowned upon by DOT.
The flail bounces over anything it hits and the knives fold up against the drum to protect the unit. If it hits something it can't bounce over, it spins the belts offering add'l protection to the powerline.
The flail cut is much better than a rotary at the cost of speed. Low grass is where the flail rules.
I was using gates belts after burning up the first set going someplace I had no business running a flail (making a trail through really thick pine plantation). I burned up the gates belts very quickly and contacted agri supply after burning up the 2nd gates set for a recommendation. They sent me a complimentary set of PIX belts. PIX was on the machine when they shipped it to me. Good folks to deal with.
I really like the flail, but I can't cut as fast or chop the big stuff.