In my small 4 tub 32 quart rack I used the 11" Flex watt. One 12" piece under each tub. This works very well. Now I have to go back and remove the double rows of 4" flex watt I used under my 41 quart tuba and put in a piece of the 11" flex watt. For me this will be a little bit of a chore as I have to remove a couple risers from the steps I built my rack under to gain access.