I have an older model Dewese hillside mower, with a 20 HP kohler motor on it. It has limitations, it does not like rough ground, it hangs up on ground hog holes, and ruts. It also does not give as good a cut, as a regular mower, as the deck cutting circles are very large, (36" per spindle) it is also very heavy, and that adds to the hanging up problems...
that is an awesome machine - seen something like that before, but it still might get my puck-o-meter to see red !
Not all that expensive if you had a lot of banks to tend to, wonder what it is rated for as max sideways angle?