Dave: I don't pretend for one minute to be a camera engineer, but I feel that any reflective surface in the path of the optical image can be degrading. With a bag bellows, the majority of the bag will be on the outer edge of the light path, but where it meets the camera body it can be quite close to the light cone. The effect may be slight, but can cause density problems at the edges of the film. Ansel Adams wrote about internal bellows reflections with his Ansco view camera due to the small size of the bellows. I have experienced the same problems with my own Ansco view camera. A good lens shade is a must. With a bag bellows and a lens with a large circle of coverage, I think you might have problems with the reflections from a shiny surface.

Regards,