Kevin,
Thank You the time you have taken to provided all the informative video you have.
I personally have benefited from many of them.
This is building log I wont miss for nothing in the world.
Unfortunately I do not understand the small jig / tool on the last photo ..... maybe you could explain or also show in a different angle (especially the grey element)
The next video will explain all. The jig is a series of scale slots meant to hold pieces of wood to specific size To allow me to plane the sides. The slots are at 1:48 scale. So the no 10 means it will hold a 10” piece of wood at 1/4” scale or .2083. The grey piece was a piece of scrap that had a 9” hole drilled so as to check the diameter of the tube i made. I would sand the tube until i got a tight fit, then fit it in the model.