Bank Insulation Test Fit

After reading a few posts about below grade insulation I've found out this brand of insulation soaks up water like a sponge. -_-
But it's R-value per square inch is too high and space is too limited and... I have big sheets of extra cheap thin painters plastic that I'm just going to spray mount around each of the 5 pieces (5th being the base piece). This is just an in ground test fit photo. After this photo was taken I spray glued some strips of heavy duty tinfoil on to the ends of the uncovered insulation. It might help hold the heat a bit. Once I seal up the cracks with some expanding foam I'll be ready to install the set up for the heat sink venting.