I see what you are getting at Stephen, or most of it. I use a enlarger to expose my film but I put in a lens with a shutter so that the times I would suppose is relativly accurate. While there is a strong talk about accuracy here I believe if one is pretty close the parameters should cancel each other out on average.
Though there may be problems here and there or even false results, by seeing the collected data one does get a knowledge or feeling how ones methods work. This will get us what we want.
I feel comfortable when I test my materials.