I am thinking of making a rack this week, the rack will be 41 qt tubs and this is my first one made with 41 qt tubs. I am just wondering if 2' w X 3' l would be a good size to have the cuts made for the "shelves". Also 4' high should be plenty of room for 6 tubs correct? I calculated 6 1/2 to give some extra space so I took 6.5 times 6 and came out with 39 so 4' should be plenty for 6 41 qts and maybe some additions later on right?