I have used Styrofoam. This is the white bead board. I cut it to the thickness you want. $20 for a 2" x 4'x8' sheet. $30 for a 3"x4'x8'. $40 for a 4"x 4'x8' and so on. At this time, I have a large amount of used dry Styrofoam that I can cut to the thickness you want. It is dry and good for your projects. Contact me for more details. Please no text or emails. show contact info