I use the Havener caster wheel sulky on a Scag 36" hydro, 16hp. They are built very well and one thing I like is the quick release pin where it mounts to the mower. You can attach/detach the whole unit in 2 seconds if you want to mow very steep hills without it. It is also pretty easy to chain it up to the bars using the hole drilled in the platform but it is kind of heavy.
As far as maneuverability, one of my guys weighs about 190 or so and mowed a pretty steep decline using it with no issues turning.