Rebuilding rear seats in DD

I have an older Moomba Outback DD, and I'm thinking about rebuilding the rear (where the seats are) to accommodate some built-in ballast.

You can kind of see the seats in the pic below. I'm thinking about building up a "platform", just big enough to fit a custom fly high sac. Then reattaching the seats to the platform.

Has anybody else done this or seen it done? I'm looking for some inspiration here.

http://www.wakeworld.com/MB/Discus/messages/3183/577634.html?1210260088

I did this in my old DD MC as well, but my 'sunpad' extends up to the motor box. Nice little ledge there on your motor box, i'd consider resting it on there, maybe take the cushion off. I put gas hatch supports on mine so it holds itself up (pretty heavy) and stays down when its supposed to. Also built in a sac box in mine as well.

On a side note, 4 ladies can fit on there comfortably. Thats good to know IMO.