When you aim, your sights are always dead center on the screen.
Hold the aim button down, and take a marker and mark the reticle on your screen. If you mess up the placement, or don't like it, it wipes off instantly with rubbing alcohol, at least on my glass screen.
It's much less distracting, AND MORE HELPFUL, than almost anything else on-screen.
I used a black marker, so it doesn't help in dark areas, so a colored one might be better.
Next time I play I'll put a dab of whiteout in the center of the marker dot, and it should be perfect.
It helps most with shooting from vehicles for me so far.