Nice mod. 2 questions:
(1) Why not use the original, trim along the lower edge, and add a small strip of sheet metal for the cutoff? That way, the distance between the lens and reflector bowl won't change.
(2) There is probably a change in the beam width intensity profile when moving the cutoff down (as you indicated); the reflector bowl has a somewhat ellipsoid profile left to right. So, even though the distance lighting is probably improved, the side beam may look different; I'm thinking in the context of the different regions you drew out as projected on the road in another thread.