I am in the process of building a water dragon vivarium out of an old TV armoire. I am trying to do this as inexpensively as possible, and am making use of several of the "shelves" that used to be a part of the furniture. The lower back panel is made out of one of those shelves, which fit snuggly in place above the TV when it was used for that. Apparently the furniture is not quite square, because when I installed the back panel, it leaves a significant gap on one side.

Do you think Great Stuff foam would be an acceptable way to fill that? I was planning on building some ledges out of the stuff anyway.