After unfolding, and a good amount of detailing in Inkscape, I can start cutting paper. Hooray.
You have to like rolling tubes:
Everything is formed around that 1/16in brass tube with a little "invisible tape" wound round to bring it up to size. I found with the Flying Merkel that what worked for me to produce the "curved" tubes was first to roll them straight. Then I cut out the lens-shaped pieces with a scalpel while the tube was still on the mandrel, slid it off and formed it up.
Not perfect, but not too bad.
The tank and box formed up quite nicely,
and it all came together.
There are one or two small glitches where the tubes join, as I rolled them a tiny bit too small. Also the lining comes out a bit too bold in the photo, though it looks OK on the model. I may correct these with a second build once more of the design work is done and verified.