They were $24, and that was a separate budget. Should have said... I have the tubs already, at the dimensions listed in the opening post.

The $50 I have now is for the rack itself. Then I'll be figuring out how much flexwatt I need and taking that $ out of another source. I already have a t-stat for it.

Most likely, I will be going with the plastic utility shelving since it's light, easily assembled, and cheap. Now, I mostly wish to hear if anyone has had any problems with those shelves, such as with putting heat tape on them. Maybe someday I'll be able to afford a good, professional rack.

Thanks all for your help!