As an owner of an RS-A1, I am trying to figure out the problem. Are the Zu mounting holes threaded? I had a heck of a problem mounting an Ortofon with threaded mounting holes on the RS-A1, because the headshell holes are also threaded. So I am guessing that this is your problem. I ultimately took some conventional mounting screws and trimmed down the heads with my Dremel tool, so I could insert them upwards thru the Ortofon and then thru the RS-A1 headshell whilst clamping them firmly together and using a jeweler's screwdriver on the now tiny slotted screwheads. I got a "sort of" firm mount that way. The RS-A1 headshell needs a re-design.
