New bellows of non standard sizes.

[alex_holden]

Using this calculator I get about 33.8 square inches for a 6.25" AF hexagon, 32.4 for a 6.25" octagon, and 37.7 for a 6.75" octagon.

[Sandy Winters]

You are correct (nice website calculator). I was wrong (That's twice)...but still nowhere near the difference that Geoff was calculating, 32 sq. inches vs 25 sq. inches. That's what jumped out at me cuz I was sure that couldn't possibly be true.

 

More concertina minutiae 

[Wally Carroll]

For anyone who is wondering why the hexagon in this example has a greater area than the octagon (and I admit I thought this as well reasoning that an octagon is closer to a circle than a hexagon) it's because the circle you could draw around a hexagon with 6.25" between the flats is larger than the circle you could fit around an octagon with 6.25" between the flats.   So even though the hexagon fills a lower percentage of it's circle, it still has more area than the smaller octagon.