Harry,
I have never tried this, but in theory, you should be able to do the same thing as the Gent with a Retro using a little improvising.
If I wanted to do this, I would start out with a strong, non-marring material like hard maple. I would take a couple of 3/4" scrap pieces with two good square edges. I would then glue these together with white/wood glue using a piece of paper between them to make it easy to split them apart later. Once dry, drill your hole that is tight enough to capture the trim ring in the center of the joint in the block of wood. On one side of the block, you will need to drill the same hole out wide enough to fit the flare of the centerband and just deep enough that there is only the thickness of material equal to the flat area between the trim ring and the start of the flare. (This needs to be pretty accurate drilling).
This will account for the Retro profile instead of just making a tight fitting hole like you would do for the Gent. Once done, split the two pieces back apart, and you are ready to remove the centerband. To remove the trim ring, you will clamp the two halves together under the trim ring so that they can catch the ring to remove it using the procedure described in the other thread.
As said, I haven't done this, but it should work. Good luck.
