so i am building my new rack/enclosure stand, and i have a ? on the spacing for the tub with flexwatt on the bottom? how much space do you guys leave in between the tub and the shelf above? i dont have any flexwatt yet so i cant lay it down and then put the tub down. just need to now how much space i should leave. im using 41qt tubs and will be using 11inch flexwatt.