About two years ago I started to correct my own sight defects - existing farsightedness - on my pistols through optical devices, like red dot systems. In this course I found out that due to the moving of the rear sight in front of the ejection window or in the rear of the ejection window the sight quality - clear view of rear sight - was improved. A further positive effect is the quicker target aquisition. In my experience the shortening of the sight line has nearly no consequence for a quick shot over 15m. There's also no problem at a distance of 25m. It is only important that the width of the chink of light between front and rear sight is very tight, whereby also at a distance of 25m the same hit image can be scored, as this is the case with longer sight lines. At Caracal the models with shortened sight lines are called "Quick See" or in common speech "Quick Sights". Suchlike pistols can be seen on Caracal's homepage. I want to point out that Caracal has a patent for this so-called Quick Sight, however only if the rear sight is placed in front of the ejection window. That means rear sights, which are placed in the rear of the ejection window - close to the impact face - don't concern the patent.
I modified my Steyr S9 and M9, as well as M40, S40, M357 in to the effect that the rear sight is equipped behind the ejection window. Also I made an "own" variant of 1911 with shortened sight line.
If pictures of them are requested, I can show them.