Just finished a 12qt rack. I had some leftover melamine pieces from some bedroom shelves I picked up when my aunt sold her house. These were the top and bottom pieces from the shelves. I had 12' of 4" flexwatt laying around. I had to go pick up the pre cut legs at lowes this morning while I was out. They ran me about 10$. It will house some 12qts for my hatchlings that are getting tight in their 6qts. I may try and find a tub that fills it out a little more.
This will be in my 82 degree snake room, an open design won't be a problem.