The problem with gunsights is that the same sight appears diffrent, in diffrent planes. In an A6M the same sight calebrated for a D200 shot in a P-51 will be calibrated to a D400 shot when viewed in that A6M.
I make my own sights with Paint, and have to do extensive testing both offline and on, to get them to where I'm happy with the sight picture, and calibrated to my prefered shooting convergance.
FW's look different than 109's, F4U's look diffrent than F6F's, every model line has a diffrent sight picture. On some planes a horizontal bar is just thin enough to dissappear yet on some planes it is to thick. It is a nightmare. No one sight can do it all, except maybe a single dot like the one above.