Jedrek,
The short answer is that transplanting a 65mm onto the standard 6x9 folder configuration does not work, nor is it possible without a tremendous amount of custom metal work. I design, build, and shoot with customized 6x6 and 6x9 folders (primarily the Agfa/Ansco lines) that incorporate many different components from diverse camera bodies. Like you, I wanted a simple and lightweight wide-angle 6x9 for my walkabout all-purpose camera. After a couple of years of work, I ended up with a few versions that do away with the folder configuration completely. The lenses I use are a 65 Mamiya Press lens, a 65/8 Super Angulon (smaller,older chrome version circa 1960's), and tiny 65/6.8 Angulons mounted on what is essentially a box constructed where the bellows used to be. Because of the difference in shutter dimensions, and as a result of many iterations, each has a different focusing mechanism assembled from various donor camera bodies or helical devices. In other words, the design objective of having a 65 mm lens on a 6x9 requires fairly extensive modification, none of which preserves the unique benefits of a folding camera.