The Beckman parts have a trapped o-ring so the rubber seal should never get pulled into the bench in normal operation.
Agree that the walls of the bench will move around a lot. The guy who did the MSD bench originally added at one point a "all thread" rod and a couple of plates to keep the walls intact. You could see where the rod was not straight in one of the pics.
I am a firm believer in making the bench strong by using a lot of support
parts or by a well thought out bench design that has minimal surface area that is not reinforced.
Tom V.