Thanks for the suggestions.
The table is a DIY macro table made from 3/4" structural pipe with a 2"x4"x3/4" plywood top. On top of this sits 12"x18"x5/8" steel plate on which are bolted 80/20 aluminum beams holding the Wemacro rail and camera.
Since the plate is oriented along the long axis of the table, there isn't a lot of room along the length of the table to mount things.
I have a wooden bar mounted horizontally to the pipe frame along either side using pipe hangers. I use these to mount studio lights mounted on microphone boom arms. I'd like to be able to use those bars if I can get enough distance from the subject and diffuser. I don't need a big range of movement, just enough to align horizontally with the subject and have enough separation from it.