You will probably notice the plates under the legs. I got to thinking about what my wife was worried about about the table falling through into the garage, so in order to distribute the force a little more evenly, I cut 12" x 12" plates out of 3/4" oak plywood and put them under the legs. This effectively cut the PSI force down by 75% by spreading that weight across 144 sq in instead of 36 sq in. Also it gave me a hard surface to shim to instead of the carpet. So I centered the table side to side and left myself enough room on the head (window) end to shoot from. Now came the slates!!
Great idea with the plywood! Let the table sit for a while to flatten the carpet out before leveling or it will go out of level quickly.