The central clamp is absolutely necessary. Otherwise the record just flies up and sticks to the vacuum arm. Much easier to turn the record around by the clamp than by the platter or the center of the bare record.

It's a piece of 3/4" mdf cut with a router and circle jig, with a piece of tool chest drawer liner glued to one side with 3m spray adhesive. It's not easy getting the center hole right, it's basically 5/32" but in this case the black rubber layer is what's really gripping the spindle.