I've always liked the AWB wind stabilizer in such situations even though there's little or no wind. It of course "locks" the front and rear standard together. I'm not so concerned about slop, flop, or whatever provided the front and rear standard were doing the same thing together. It's easier than the "4th leg".
You should check the shot too. You'd swear my old Korona 8x20 could never take a sharp picture, and people complain about Canhams being limber, but the Korona and Canhams (at least the one I had) consistently produce great results. If the whole camera is wobbling around the tripod attachment, then the standards may well be staying in the correct position relative to each other.
I've never used a Bogen 3029, but I can almost guarantee that an 8x10 isn't going to be very stable on that small a platform. You might also check that the screw isn't bottoming out before the camera is really firm on the head.
Cheers, Steve