Aperture (peep) sights are a tool of the rifleman, a windfall to the older rifleman. In my 40s and 50s I competed with peep sights on rifles, and occasionally hunted with the same guns. I used a Merit adjustable diopter disc that threaded into my tang sight base. When deer hunting I would keep the Merit disc screwed into the base until the light got low, then I would screw it out and drop it into my pocket for the remaining minutes until legal shooting light was gone. I could do some very accurate shooting with the disc screwed out. AS Gil said, when you focus on the front sight the eye automatically centers it in the "ring". Doesn't matter what size that rear aperture is, up to a point. One quarter inch is plenty small for accurate shooting out to two hundred yards or so. Most ghost rings, for rifles, are no larger than that, IME.