[pinhole-discussion] Body caps?

[CJ Rumpolo]

Hi, I am just starting to dabble in pinhole photography and was wondering if
someone could offer me an answer  to a question or two. I want to try to
drill a pinhole into the body cap of my Bronica but I do not know how to
measure the focal length of the body so I can drill an appropriate size
pinhole. How do I measure this distance. I am guessing it is the measure
from the film plane to the inside of the body cap. Thanks in advance CJ.