Seems like not many members have flails!
I used PTO toppers when I was in Northumberland and then Cumbria. I used flails and blades.
I did look at quad toppers but was put off by the separate engine thing.
We now have a very meaty ride-on mower here, as we have holiday cabins and a campsite so need lots of mowing - not all on "lawns", lol - which can top to some extent. I also have a scythe, which is fab for small patches. (Not least as I like to reduce not decimate, and leave a patchwork of surfaces for wildlife and livestock to make use of.)
[member=26309]jaykay[/member] used to have a 20 acre (I think, or maybe it was 12) smallholding in Cumbria, very rough / reshy pasture, and used a towable mower (blades not flail, I think) with a Briggs and Stratton engine. She found it very capable on her fairly rough terrain. Sorry I can't remember the make she had. ETA did some searching and found it. She had a Quad-X wildcut mower.