I put an Aerial Airborne tower on my boat this winter that I bought new off of ebay for $640 shipped and I'm pretty happy with it so far. I've been out about 6 or 7 times now and it's doing well. I think it was a very good deal and I would recomend it.
I have a rope hook between my swim platform and the back cushion. When I'm behind the boat the hook is probably only 2-3 ft off of the water level. When I'm jumping it seems to pull me back down to the water instead of letting me fly. And mike I use to have one of those hooks when i use to ride behind my bass boat before i bought my Sea Ray and that keeps the rope even lower to the water.