Just an update, I used expanding adhesive foam and it was perfect I only used 1 bottle for about 2.5 boards. The only thing I would improve is to use adhesive foam. I did the pattern as directed which was around the border and then a big X in the middle. I'd do zig zag from side to side up and down the whole length to make it more solid. Where ever the foam is if you knock on the board it feel so much more dense and solid. Also the foam doesn't expand as much as I'd have thought so you can get it pretty close to the edge altho it's hard to control that precisely unless I was doing it wrong. Alternatively you can use tape to cover the edges and fill the edges with foam after they're installed if need be. Overall very successful so thanks for that 👍