Ooooh! My thermometer doesn't have a probe but I do lay it as low under the substrate as I can. My only question is, the thermostat can only regulate up to 95 F. So if that's the warmest it'll allow the mat to go, won't it be too cold inside the tub, since it has to heat through plastic? The tub has a slightly ridged underside so the mat can't lay completely flat against the plastic and I'm worried it won't be able to heat it enough.