ask away!
no, the heat tape should not be able to touch the tub (TBH i'm not sure why, but i've always read that they can't touch each other). the rack i just got has a ~0.25" x (however wide the heat tape is) groove cut into the bottom so the tubs just slide over the groove over the heat tape.
i haven't figured out how i'm going to cut the groove yet. my father is a carpenter so i'll have to ask him and see if he has any ideas on how to do it.