I have 2 of the Attwood 4.5" SS cleats (linked below) that are still in the box. I bought 4 initially, but decided I just wanted 2 in the back and that the rare times we do tie up I will use the tower legs in the front. If interested, I'll sell them both for $60 plus whatever shipping is.

They were pretty easy to install in the back - plenty of room to get underneath.

http://www.boatersoutlet.com/4-5-in-ss-neat-cleat.aspx

cleat.jpg