Installing new 23 gal. belly tank in 18' Chieftain OB

I have a question about mounting my poly belly tank that I'm planning to sandwich in place with no clamps and concerned about expansion vs rigidity. It fits between the stringers with about 1" clearance per side so 1" foam fills the gaps. I made wooden platforms to support the weight on the 2 tapered sides on the bottom making the top of the tank almost flush with the bottom of the deck. On either end I have aluminum angle rivited between the stringers and the tank fits snug between them. The The bottom middle of the tank has a large obvious bow that smooths out about half way when filled with water so there is expansion space even if I put more foam under the middle flat section. Does sandwiching it in place as described sound like a reasonable approach for installing this 23 gallon tank?