I don't do that with my melamine vivs. What I do, is tape cork floor tiles together, to make two mats the same size as the base of the viv. I then cut out the shape of the UTH at one end of the cork mats (where the warm end of the viv is needed). I put the "whole" cork mat on the floor/top of the viv underneath, the "cut out" cork mat on top of that, the UTH in the gap cut in the top cork mat, then the viv on top. It creates just enough of a gap to allow air circulation, but not so much that the heat doesn't reach the floor of the viv. I'd still recommend using a thermostat.cut out some of the melamine as suggested