While still deciding whether to take a little more off the cylinders (which I am leaning towards) I decided to do a dry fit of the cylinders, slide bars and the inside slide bars/ cylinder front to make sure that all fitted snugly but freely.

The outside cylinder unit, screws in place and I had deliberately not fitted the frame spacer that it fits to, until I was at a point where I could determine whether or not I needed to modify it to allow the inside slide bars to fit.

As it turned out I did. I needed to cut a slot out of the middle of the spacer between the two nuts.

Now I could have done it with the piercing saw but knowing that I would never have used the piece that I cut out, I found it far easier to pop it in the vice and mill it out.

Next, I added a representation of the bottom to the inside cylinders and then assembled all the parts to the frames to check the fit.