In the late fifties I earned my living as an Architectural Photographer
using a Gandolfe half plate camera, pin holes were a real problem the way
we solved this was to use Bostick which was then and is now a commercial
product that was rubber based, the method was to stretch the bellows to
maximum extension. Then take a blob of this gluey black glob and stick it
in the hole. Amazingly this technique worked. The rubber cement being
flexible stretched and shank as the bellows moved making an effective
mend.We found the holes by putting a light bulb in the camera and covering
the back with a dark cloth.
pete
Ps
I still have a camera given this treatment for more years than I like to
admit too, which is is working perfectly.