So many things have a effect on this it is impossible to pick the perfect height. Tube size, frame diameter, floor thickness, amount of inflation. and to a small degree how much weight your carrying. Change anyone item and you change the perfect height tab placement. Do you want 1/2', 1"clearance or something else. I go for More inches from frame rather than less and add shims if I need less drop (I.E. need to raise the box).
Time is like a river. You cannot touch the water twice, because the flow that has passed will never pass again. Enjoy every moment of life on or off the river.