Good foresight with thick substrate decreasing UTH effectiveness. I put a light layer of substrate in the warm side hide (not even enough to barely cover half the surface area) just to give a bit of absorbency. You can pile up the substrate everywhere else since most of the time is spent in the hide. I also use a lamp to maintain ambient temperature. I use aspen and coco-choir mixed. The aspen can be dusty though. Cypress is great at retaining moisture if you plan on using a lamp, but there are usually large sharp pieces. I know many people use this with no negative effects but I tried it and didn't really like how sharp it got once it dried out.