My matchbox PH's shoot at about f/90. Aperture can make a difference to a point. I think the quality in the hole edges make much more difference. If the light enters the camera through a smooth-edged hole it takes a more direct path to the film and creates a 'sharper image'. So I wouldn't worry too much about the size of the hole unless you want to know what aperture you're shooting at. But why make this thing technical, right? Kinda defeats the purpose, in my mind.