> Also, if by their extenstion below the pot or their outer diameter, they may also serve as a windscreen to the pot / fins.
Yes, that was part of my thinking too.
I'm now part way through extending the HX height, adding exhaust ports & blocking sections, with a view to adding Thermawrap above this, making an HX & insulated pot.
Simple aluminium flue tape could be used to surround the HX, to add a bit of stability if needed.
And I've been looking at high temperature doubled-sided tapes for bonding the HX, e.g. 3M 9640PC tape.
 d'oh! whilst it's easy to add exhaust ports to the outer triangle, it's not so easy to add exhaust ports for the inner triangle. So I'll abandon that cunning plan...
ps. how to make it? tediously, I suspect... That was one of the downfalls of the SqueezeBox, which had two, opposing folds so was even harder. But I think a simple concertina fold should be possible using conventional packaging manufacturing techniques, even if I can't point you at exactly how to do it... I have a sketch with six pins in front of me; make folds around pins, shift & repeat; two pins provide alignment, and the other four are used for the four folds required per section. I've thought about moving blocks, too, hinged around the 'can centre'.