peregrine I'm confused. How does a M54f adapter connect to a M54f camera?
I think the idea is to bolt said adapter directy using 4 screws to your camera.
Check the mechnical drawings to see if the adapter screw holes match the tapped screw holes on the tilt plate of your camera.
The open end of the adapter then forms a female M54 flange that is an extra 15mm away from the top surface of your camera's tilt plate.
Check the photos in the document that was linked for you.
Notice that the camera angles are properly aligned, instead of using threaded tubes.
Chen