I think 2 part foam would help you get a good form so that you can glass in the gaps. As for pool noodles... I put those in my ski for Daytona. They don't hold a lot of water but they do hold water. I was able to squeeze water out of all of them and I'm beginning to think that's why my ski was riding wierd after installing my new pump. What about just installing the smallest versiplugs in the tray and running nothing in there? Water will get in there no matter what you do but if you can keep it drained, any weight that gets uner the tray will be less than any foam.