I just built my first rack. I was wondering to I lay the heat tape directly on the plywood or does something go between the 2? Also do I lay the tubs directly on top of the heat tape or should there be a small gap between tub and tape? Last question I hope my tub is 33 1/2" long so would a piece of heat tape 12" long be to much? THat would leave 21" cool side I guess?