What are you thiking of doing? using tubs with the plastic tops? how will you build the heat into it? how will you keep the heat in it?

I would recomend you do make a COMPLETE shopping list of all the things you will need. (the shelves, wood, flexwatt, tubs, and everything else) Then get a good picture in your head of what it will end up looking like. Think about how hard it will be to regulate the temperatures on each level... keeping them all right. think about the total cost

Then go to rbi and check out their ready to go, heat built in racks that include free shipping. 9 times out of 10 when you consider all the costs involved, the RBI racks are a little more expensive. but look at the difference in what you end up with at the end.

just my two cents.