This is what I started with.
I added this ply to the top. The grinding was done before I found it.

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The knurled nut rubs an locks against the top of the ply.
This took some play out.
It is a very tight fit but I added a bottom too.

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I changed the post to a thread and added 2 locking nuts.
I ran out of time waiting for the glue to dry.
There will be a 3rd bolt at the front so that I can lock the height at 3 places.

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