I assembled a 5x4 format camera a few weeks ago. The film to pinhole distance is ~39mm, and the pinhole is 0.3mm. To a certain extent the coverage is governed by the thickness of the material used for the pinhole. The thicker it is in proportion to the hole diameter, the smaller the coverage. Then there is also the amount of corner light fall off that you can accept as coverage.

My first pinhole was too thick, and I had a roughly circular image on the 5x4 film. The current one is much better and has (weak) detail in the corners. I'd say that there should be no coverage problems with a pinhole to film distance close to the 'normal' focal length for the format.

There's a negative scan of the first image with the camera here: http://grahampatterson.home.comcast....d-building.jpg The fall-off in a print is not quite as pronounced. You can see the darkslide being used as a shade in the top left corner 8-)