Here is the seat base from the top side. OUr next little variation was to use welded on strengthening ribs instead of rolling a bead into the base. We could have rolled in the bead, but would have had to tool up for that with a special roller since it is so close to the turned edge of the inner holes. This ALSO turned out to be better – as you could tell it made things ALOT stiffer down here – especially since the stiffener we made was in thicker 18-gauge steel.