I have already built up three bellows by myself on the past .
one for a 11x14 camera (the rear standards size has the same square size 35x35 cm) ,and one for a 7x17 camera .
The problem I have met with the 7x17 camera is that the size of the rear standard is not the same.One size, of course, has to be more big than the vertical one so the bellows corners don't fold perfectly like the 8x10 square size .
The corners infact are not perfectly on line and this make the bellow more thick ....
Looking at the drawing of this we-site (formula to determine the widht of the web):

http://www.cyberbeach.net/~dbardell/bellows.html

it says" With a plastic 45' triangle draw line down from the 45mm line, draw a second line from the 90mm line up at 45'.

This little triangle provides several bits of information. As illistrated above, measure from the point of the triangle to the 45mm and 90mm lines, this is the width of the 2 webs (24mm and 21mm). From the point of the triangle to the line which represents the length of the panel is the space required between the panels....."

Question:Which of the two panels for a 8x20 " camera I have to consider?
I tried to conatct the guy time ago but it doesn't reply but it's still useful his info.
If someone already experienced this problem any useful word will be appreciated.My wish is to make a bellow as good as possible.
I reapeat, for the 810 or 4x5 format with a square size standart not problem but with a 7x17 (45 x 25 cm standart size ) or a 8 x20 ( 57x 35cm standart size) this is very more difficult , but not impossible...
Thanks