Do you recommend 3 or 4 posts under a shelf?

Support shelves with three posts instead of four. Four posts cause the shelves to wobble unless the bottom of the kiln is even, the shelves are flat, and the posts are exactly the same height. It is best to position posts fairly close to the kiln walls and away from the center of the kiln bottom. This places the weight of the kiln load close to the kiln stand and away from the unsupported kiln center.