Hello all, I am looking to fill in my large columns/pillars with polystrene, the owens pink stuff. but am wondering if 1/2" would be okay to use? if I coat it with some drylock, I thick it would help, but not sure if the 1/2" would hold up in the elements here in SW Missouri. I don't want to spend an arm and a leg this year for foam. normally I use pallet lumber and cut it down to make it look stoneish with my tablesaw. But I do not have enough to go around this year. So was looking at other cheap alternatives. I have my frame built, just need to fill it in.