It may be only 2 inches beyond the cowls extreme edges but there's still lots of prop working for you as the cowl is tapered. The only time this would be an issue would be if the cowl was a end on bucket like a large radial cowl and there was no way to let the air out the back. Then the pressure would build behind the prop disc and you'd have a problem.

You see props work through two mechanisms. At rest they accelerate the air back and move forward. But at flying speeds they actually screw their way through the fixed air and generate a less energetic slip stream than at rest.