It's time to get jiggy with it, and we've turned to the longer lengths of alloy here so as to arrange them four-square using a set of, well, set-squares that do what they say on the tin. Note that the ends just kiss each other rather than overlap, because the tube connectors will go that last mile. Well, inch actually. Looking at the image at centre it can be seen that I shot myself in the foot with that 38.125" measure for those shorter lengths, forgetting the overlap.
I've taken an inch off all round however and note that in the final picture the parts are laid out to my total satisfaction and set upon one of the two 19" sheet-alloy squares. Finally note that we should mark the margins of that centre-section with a pencil as a guide, as we are about to slip it out from under there and place it up top ready for the riveting.
