4" and bigger, it is NOT uncommon to see slivers of light showing at obtuse angles. In practice, it is almost certainly not any problem at all. I use a 4.5" Shutter ALL THE TIME, and have no trouble, not in the least, even though these slivers of light show at angles. The lens has a more perpendicular view, so unless you've got light sources aimed AT the camera that are brighter than whats on the subject you can relax. (and my film is $200/per shot, Polaroid 20"x24")
Reno (Mr Packard Shutter Co to everybody who doesn't know) no longer services the old #8s, they are LONG discontinued, and his bread and butter is selling new shutters. Reno is a good fellow, but I think the durability of the product is a blessing AND curse for him. I have ordered several new ones from him over the years, and also have a sampling of ancient ones, #5s, #6s, and #8s.