Living on the edge to say the least...
FWIW - Moment=RxF ; R is the length of pole and F is the weight of the little mower.
The dam mower and bar weight could be off set with a bar and weight set 180 degrees from the little mower; attached at the same point on your tractor. Match up the Moments or better yet make the M away from the water 2x. This would minimize the front tire lift and potential roll over.
