Thanks for the tip. In that case I would go with Polypropylene too. It is easy to work with. My only concern with it, and I may be all wet here, is that caulks and adhesives don't adhere to it and it may be harder to seal. I personally wouldn't use acrylic for this simply because it is so brittle. I have drilled it, cut it on a table saw and ran it through a joiner and it can be done without breaking it, but I have also seen it cracked around screws an from impact.