Interesting links, John.

The first one is about alum tanks, and is good if you have to use an alum tank, though I don't know why you would want to.

The second one has some good tips for installing tanks of different materials, including alum and plastic. I don't see why you would want to use plastic sheeting to prevent the tank from adhering to the foam, if you are using a plastic tank. The tank should outlast the boat and should not need to be removed. I would rather have my plastic tank locked in place by the foam, rather than bouncing around when it is only partly full while traveling home in rough seas.