I think both the visor and the helmet is off.
I made this image to describe the issues.
Click it, to view the animation.
Yellow is the mesh from LDD, part 30124, which is an alias of 2446.
Blue is the LDD mesh of visor 2447.
Trans red are the ldraw versions.
The simple solution is to resize the current visor.
Shrinking it is possible. It would follow the green line, instead of the red.
But the major issue would be how to handle all the other accessories made to fit on the helmet
Different knight helmet visors, diving goggles, ski goggles, space visor, night vision goggles, underwater visor, and so on...