Years ago Mark Larson presented via pictures to this board some original examples of how he extended length. Maybe he can find those pictures and show them again.

I have added a wood extension of 1 1/2" of perpendicular grain using a contrasting wood grain. American Walnut stock with a high end type English Walnut. Beretta did something similar on a few guns that you may have seen. It looked OK, maybe better than a rubber pad of the same size.

So many guns, so little time!