<FONT face="times new roman, times, serif" size=3>I used 1/2 inch thick sheets of R-Tech styrofoam (lowes, home depot) under hinged/bolted down sheets of 3/4 in Birch plywood. I like 3/4 better to fasten other stuff to, than 1/2. </FONT><br><FONT face="times new roman, times, serif" size=3></FONT> <br><FONT face="times new roman, times, serif" size=3>The R-tech made a HUGE difference for me on the sides, and should do equally as well on the floor, plus it will form-fit into the grooves of the floor. </FONT><br><FONT face="Times New Roman" size=3></FONT> <br><FONT face="Times New Roman" size=3>AJ</FONT><br><FONT face="Times New Roman" size=3></FONT> <br>