I've just uploaded a webpage on construction of a square bellows I built for a fullplate wetplate collodion camera I'm building.
Here's the URL if you are interested:
The bellows measures 11.5" on the outside with a 9.5" interior opening. It extends easily to 30" and compesses to under 2". However, I've written the directions so that any dimensions could be adapted to the procedure for other designs and requirements. I've also included a materials list as well as rationale for building the bellows along with the design considerations.
Hope someone may find it helpful.