Re: Small point
"I would guess that a flail mower is a drum with lengths of chain hanging from it, that use brute force to cut things instead of a single spinning blade."
As the owner of a flail mower (and the tractor to power it) I have to say that you are a bit wide of the mark. Chains don't feature in the design because they tend to break creating a danger of flying shrapnel. There's a rotating shaft fitted with bearings. In the UK flail mowers tend to have flimsy "Y" or "J" shaped blades that are bolted to these bearings. They scalp the vegetation and can be knocked out of the way if they hit a rock or large branch.
Italian and Japanese flail mowers tend to be much more rugged and have hammers that look a little like an old fashioned adze with a sharp leading edge. These devices can be regulated for height and are capable of cutting wood up to about 50mm in diameter. Same bearing arrangement but the mowers are designed to achieve a lawn finish even when cutting grass up to 5ft high.
The underside of the mower looks like this: Flail mower hammers.