has any one used...

the single bar and cable towers made by joystick or fly high, i have an I/O so i figured one of these would put less stress on the hull but would give me the same pull of a tower.

My neighbor has one, and it's fine.

I have a Fly High Monkey Bar on my I/O and other than a little spider cracking of the gelcoat at the base, it works just fine. If you use a travel cover when you're on the road you may want to split some tennis balls and put them over the uprights on the bases to keep from putting holes in your cover.