After riding in a friend's MC Prostar, I have an idea for a rear seat mod that i will do over the winter. The mod will remove the three cushions and frame and replace with a one-piece bottom cushion that can be slid into a low position or slid over hand rails to make a large sundeck. In the low position there will be about 7" of storage under the bench (I am raising from stock seating position) and in the deck position will povide a place to put a filled fat sack.
This will require making a new fiberglass frame for the bottom and back rest. Also will upholster the back rest. Plan to raise the rear ski locker pad about 1" to make it level with the rear seat in the sundeck position and to provide more storage in the ski locker. Will post pics as I go.
Google Master Craft rear seat 2006 Prostar and look at the pics. You'll get the idea.