@Vitaliy_Kiselev

I'm just discovering other advantages besides killing much more unwanted stray light:

1. Yes indeed. it does turn out to look extremely cool - and I can't say I mind that :-). (Sort of like a DSLR in a dinner-suit).
2. With bellows closed, it packs down really flat into a small case so I'll be taking it places when a matte box would have been too big;
3. I'll work much faster than with a fixed hood & flags.

@DaleCampbell

Is it a pain to focus with the bellows on?

• The short answer us yes - it's as hard as any matte box.
• I'm doing this as part of my "let the camera do the work" trials;
• You could actually set most lenses back further than I've shown, using some sort of cone-shaped donut or adapter;
• You could add a focus lever-thingy;
• Thanks for your input! (tell me if you can think of an elegant way to add a French flag without drilling into the bellows. (remember I'll be adding a slide-in metal letterbox matte; the lens will be in a Ned Kelly-style bunker. Without a small flag, sunlight will hit the upper edge of the slit.)