After using the riser for a week I decided to maker a couple of small changes, then sand and finish it.
Pass through holes for cables 
For both above and below the desktop 
Some leather scraps glued to the back to prevent scratching wall paint. 
I used a short length of black pipe to act as a spacer for the mounting bolt. I thought about cutting it off but I might change the mount later so I used a spacer instead.
I sanded it down and threw on a couple of coats of oil and wax.
It’s nice to get the cables off of the desktop.