After a small hiatus, I have finally bitten bullet on the pompoms. In Pontos' later Duke of York upgrade they provide resin breach components, which makes them a lot easier.
The Academy pompom parts in the sprue, to ne fair they are quite good.
What is used from the main part of the mount compared to the total unit
The brass frame for the breach assembly.
The bases, one brassed up, the other straight off the sprue.
As far as I have got with one mount, the fact that the plastic breach section is not solid at the front end makes drilling out the barrel mounts a touch tricky.
To make my life easier I shortened the mounting pins on the barrels
A beginning of the layout of some 20mm, to my surprise and joy the first cradle fitted straight onto the pedestal, in past experience the hole in the cradle is too small.