So, I'm a little confused. Ben Gee. I do have to raise the tray, so I was originally going to place some OSB3 on top of some new 4" X 2" joists. I was then going to sit the tray on a bed of mortar on top of the OSB3. However, I thought that the legs would be much easier, especially with such a heavy tray, in a very confined space. But then started thinking on a 1200 X 800 tray, how do yo get to the rear legs to adjust them accurately? The last time a set up a pulley, fastened to the joists above to carefully drop the tray in under control