I am putting together a tub enclosure for a new addition and got to wondering about the UTH. Do you put the UTH directly on the tub? It won't get so hot that it'll melt the plastic so long as it's on a proper t-stat, right?

And I read over Vvpyrz's sticky about this and he described building a "mounting board" for the UTH. In other words, you can mount the UTH on the board and lay the tub on top of that. Well, I thought the UTH had to breathe underneath. I'd like to use a mounting board because cleaning will be easier, but is it safe to sandwich the UTH between the board and the tub like that?

Many thanks!