A smaller ap is more accurate. Nope, the eye still centers the front, the width of the front has more effect on accuracy.
Hmmm, not quite.
The smaller aperture does two things (1) it sharpens the image and (2) it forces your head/eye alignment into a smaller arc of error. If your sights are set for target style work, the width of the post doesn't become a hindrance until you have to judge holdover. And if you're trying to shoot the 45-70 at 200yds, holdover is an issue.
The key factor is consistent head position. I.e. you need a repeatable cheek weld. I put a big brass tack on my Guide Gun to be a "kisser button". I've used the Williams Firesight combo for a long time and it is very fast and accurate to 100yds. And it isn't as clunky as the 5d.
