Another thing I did to a 3047. My old 3047 is about as old as yours. So I recently picked up a mint newer model to use as a backup and put it on my backup 3021tripod. Yesterday I had to do a test shot in the backyard and decided to use the backup head and tripod. I noticed that camera was rocking slightly on the head. Not locked down tight enough by the spring loaded arm. Then I noticed that the arm angle was slightly CCW so it didn't fully engage the release plate when sprung into position. I took off the allen headed bolt on the arm, pulled the arm off and noticed that it had splines that engage the lower piece. I rotated the arm CW so that it looked like it would be approx 90 degs to the release plate when sprung. Put the screw back in and it now holds the camera tight when sprung. I forgot about the spring in the bottom piece so I had to fiddle getting it in the proper place when reassembling. I think you could hold the bottom piece in place when pulling off the top arm.Then rotate the arm, put it back into the bottom piece and attach the screw. That way the spring would stay in place and make things easier.
I'm really sure my head came from the factory improperly adjusted. Anyhow this may help someone with a newer head lockdown problem.