I put them straight across the beam of the boat on top of the gas tank. I took a 2x12 and ripped down a 2x10 to fit in the rear locker, I then tied them all together with 3 1x10's to raise it up off of the top of the tank.

I realize that this does not entirely relieve all pressure off of the tank, but it disperses the pressure over a larger reinforced area. I have it in all summer and have not had any issues nor noticed any kind of change to the tank when I lifted the floor up to take a look after the first few trips out.