To add to Doug's post- the line must be drawn somewhere, or folks with whom winning is the most important part of shooting, would show up with AJ Parker, Central or Redfield target aperture sights attached to their guns, front and back. Rule benders must be kept in check. Rule bending or stretching has destroyed many competitions which have now turned into race-gun events. I for one, feel it's best to keep things simple and straight foreward. Open sights, although even they can be 'streeeeetched" with the U notch to be used as an open top aperture sight as well as buck-horn-type sights used as apertures with higher than normal front sights, etc.
Not liking one of these normal stretches is too bad in my book. If you want to use an aperture due to your failing eye sight, then use one that is acceptable - open top or U notch but has to be open. I-too would like to use a match-type rear as well as front sight as it would make me much more accurate - but I also feel it degrades the 'flavour' of the shooting. Therefore, I use open sights that I can almost see. If I practise enough, I know I will be in or close to the winner's circle - sometimes - good enough.