personally i built some using the container store tubs(made by iris)
they have cstc 375(15qt) and the cstc 570(32qt) tubs. you have to play with it a bit but i got both tubs in the same rack the 32qt tubs obviously must go in sideways. also i have back heat on them with no issue
on another note im just about ready to just cover the whole wall with flexawatt and just use shelving and brackets