I shot a test roll of XP-2 Plus on Sunday with a new (to me) Bronica GS-1. The lens was one of my 100/3.5s, the back was one with a 220 6X7 insert which I removed and replaced with a 120 6X7 insert. The prints from all ten frames show a light leak near the lower left hand corner. In nine of the frames the affected area is small. In one it is larger. The affected area in each frame does not extend to the edge of the negative. The spacing between the frames is not perfectly even but it is never too wide or too narrow. When I look inside the back I see that there is no felt or foam sealing material. There is just a series of baffles. The only cause for the light leak I can think of is the space left when the dark slide is pulled out. Based on the angle of the sun in the shot with the more severe light leak I think the sun must have been shining right through that slit. I suppose the obvious test is to shoot another roll but with black tape covering the slit from the time the back is attached to the time the roll is fully wound through. Does this sound right?