I then set the tabletop on the ground, underside up, and set the bases on the plywood exactly where I wanted them, and marked the location of the bolt holes on the plywood. Now I have a depth of 1 1/2' to work with to attach the bases to, assuming 3/4' ply was used for the tabletop playing surface.
I then cut a piece of 3/4' plywood to that squared-off shape and permanently attached it to the underside of the tabletop using 1 1/4' screws. Here's what I did to make the bases detachable: when I installed these on my table, I penciled out an outline on the underside of the tabletop where these bases would attach, then added about 4' outward, and squared it off. I'm not going back to folding legs anymore!
I used 2 table bases similar to these for my table and they're really stable.
