I don't have pics yet, but I took two 40 gallon RV fresh water tanks, built a framework around them, and covered a cushion for a seat and they sit on either side of my engine compartment.
My boat is a DD, so I removed the back seat altogether and the tanks run along the gunnels of the boat a little bit past the engine cover, I am building a small bench that will fit in between them and it will house two batteries. I haven't figured out what to do for some weight up front yet though, and I am also looking for some cheap pumps if anybody has any ideas.
I used the hard tanks for the first time today, they worked really well, They only hold about 350lbs a piece, but they are placed pretty far back and they made the wake a little steeper, bigger, but it was nicely shaped.