Can you tell us more specifically what you find to be the problem? I usually do 5x7s and have never found the Paterson finder to give me a problem.
Originally Posted by Stephen Prunier
It will only work near the centre of the print. As you move it to the corners the area it shows become less and less but anywhere near the centre will be fine. Try focusing on a sharp line between a light and dark area in the print projection. You need to get the thin black sighting line in sharp focus for your eyes first. The top slides up and down for this. Then move the enlarger bellows until the grain "pops" into sharp focus and that's it.