Just thinking that it would make more sense to clear certain areas that way. Cut stuff down before you run over it. I seem to spend more time in reverse with my brush hog, just so I don't put a tractor tire on something I don't want to. I am just thinking, and it's probably more effort then its worth. Just bouncing the idea around.
That is why they mount on the rear and cut to the side, typically the right side.
Of course, you have to start somewhere and the first run does knock stuff down, but with a bit of planning you can probably cut that as your last run back, by which time it has probably sprung back up again.
Oh yeah, I forgot to mention that they fold up vertically for transport, so you can get them through gates & such.