[beeje]

I did almost the same exact thing that rohrmann did. I filled the space (with wood) above the stock u shaped supports that came from the factory. I did not add any extra supports. These tanks have a history of leakage do to there 2 piece design with a glued on top. They generally give way when over filled or driven down the road with waste in them. Try not to do either of these things. My tanks also moved back and forth so I installed some wood blocks to stop that from happening.