Shane has sent me a document which lays out the procedure for bellows manufacture very clearly. Consider it a leaf-shutters resource. I'm sure Shane would send it to anyone interested and if it's alright with Shane, I would send it.
FYI, I'm thinking perhaps I can use ball-bearing drawer slides as part of the bellows extension mechanism. There is a model which extends from 30cm to 60cm - and many bigger sizes also.
http://www.drawerslide-int.com.au/index.html or http://drawerslidedirect.com.au