Anyway, tightening that nut carefully removes the play. I backed off the friction on the bearing first (the usual hex head adjustment on the side of the mount) then tightened it back up after tightening the nut. MUCH MUCH BETTER! Virtually no play now. I can focus without guessing and the mount is now a keeper.
BTW I have also added the wooden tripod and a set screw cable-type handle for the azimuth slo-mo control. Looking for a 4" handle with set screw for the altitude.