Has anyone used expandable structural foam when making a deck extension. I am thinking of making lightwieght forms for storage boxes and a few other forms for cup holders, on deck tool storage, etc and pouring the foam. The forms can either be left for extra support, but I was curious if the foam would suffice with some resin and cloth. I would overlay with 3/4 decking. The layout I have in mind would take 6cu ft of foam and the whole deal would only wiegh about 60 pouinds done this way. I am considering glassing the 3/4" decking in as a permanent install.

Any thoughts, comments, or experiences?

Thanks Folks