Foam in place a water tank?

[mrdeepseafisher]

I am getting ready to install a new fresh water tank which is about an 1"-1 1/2" smaller than the compartment in which it will be placed. It looks to me like if I poured foam in around the tank that it would hold it firmly in place better than bolting in place. I had a friend who worked at a boat building company tell me they would plug the tank and pressurize with air to avoid the tank collasping while the foam expanded. Any feedback on this good or bad would be appreciated?