Quote Originally Posted by j_h_smith View Post
To help prevent warpage, get a 1/4 inch piece of plywood and put a back on the rack. Make sure you screw the backing into each shelf. This will add strength to the shelves and help prevent warpage. I'm not saying this will prevent all sagging of the shelves, but I always put a back on my racks. This also aides in keeping the heat inside the tubs. You use a lot less electricity because the heat is captured in the rack and transfers to the tubs easier.

HTH,
Jim Smith
This is what i do currently with my smaller rack and it works great. A whole piece of melamine is on the back so the tubs are always nice and toasty.