I agree with this statment regarding belly heat and substrate it was very difificult to get a steady ready on my tubs when I used husks as substrate. I recently switched to pre cut paper liners for flooring and belly heat is awesome I enjoy having steady reads and believe that it would be more effective with digestion just as an assumption. an assumption that comes from understanding how the thermos work and that the heat would be more directly distrubuted with belly heat. but like i said just IMO.