Pays to draft the outline at the outset and I've done so in Apple Pages, whose elements a chimpanzee could grasp. I am actually old enough to have worked with the Vydec dedicated word-processing system that could output text to the printer for an equivalent outlay of $60,000... so Pages is rocket-science so far as I'm concerned.
I like what I see, a caveat being I may stretch the central square to 50 cm instead of 19 in (because the sheet-metal supplier does so in metric).
Going to be a leisurely build, but I'll hold your hand throughout.
