It is a secret.
Also, if you want to be able to plug in new cables, rather than soldering them, find the alternative bracket with the RCAs riveted in place.
You would be best off finding a better chassis plate on ebay. They pop up regularly. As long as it is 1229 or 1229Q, and has a trimmer screw for centering the pitch adjustment.
"trimmer screw"--are you referring to the pitch adjusting wheel?