Sal: page 76 seems mostly to do with using blue filtration, which I'm not doing. I understand the difference between ground glass and an aerial image focuser. I'm not seeing too much else that helps me.
I just don't understand how four instruments designed to tell me one things provided four different answers. It would be like having four calculators, giving them the equation 2+2, and coming up with the answers 3.75, 3.9, 4.1 and 4.3. You wouldn't say "well, that's close to 4. Good enough."
I'm not particuarly young, but I was really surprised by how much sharper the prints focused by eyesight were compared to the grain focuser.
While it's much easier to focus with a grain focuser (everything snaps right into place, doens't it?) it's of no use if it is not accurate.