If that big string trimmer came with an operator, I might give it a try. wink
Since my last post I have mowed the back side of the dam twice, and even worked up the nerve to cut the steeper portions. And I found the adjustment to increase the reverse power, so I can now mow straight down the slope and then reverse back up the slope. That works on all except the very steepest portions. On those I still mow down, circle across the dam, and then mow the next row.

I would feel perfectly safe mowing across slopes as much as 15 degrees (unlike a regular ZTR), and I would bet some younger and more foolhardy fellows would mow the whole dam sideways.

I have not yet tried mowing the water side of the dam; the reverse works well, but I would not trust it there.

Another fellow on a lawn mower forum purchased a Cub Cadet that is similar to my Gizmo.
http://www.lawnmowerforum.com/general-mower-discussion/1775-anyone-else-have-gizmow-3.html
That might be an option for those who are afraid to buy a discontinued model. Maybe next year I'll get back in the sheep business, but for now, the Gizmow sure made my life easier.