I finally succeeded in constructing a mid format pinhole that is capable of rewinding the film, what's not as easy as I thought before. Not being very confident about the light tightness of the '' magic box'' I've run a film through it.
It turned out not only to be light tight, but it also managed to take some photos-photos that don't really look like they were produced by a pinhole. Just have a look at em.
Course, I knew middle format pinholes would be more detailed, but this surprised me a lot. They look more like they were taken with one of lomo plastic lens cameras. I'd better take advantage of it.