I have more difficulty on a narrow fingerboard than I do on a full width classic fingerboard. I don't wrap my thumb around the neck, as I find that badly inhibits the freedom of action of the other fingers. And I have to "squinch" my fingers tighter because of the closeness of the strings.

When you watch someone like William Kanengiser (link above) play, he has no problem at all with the full-width classical fingerboard, and as complex as "Rondo alla Turca" is to play, his left hand position and the width of the neck—and the fact that his left hand maintains a correct position throughout—make it much easier for him to play a very difficult piece and make it look like a walk through the park.

The position of his left hand is "correct," not because of someone's arbitrary notion, but because it works.

Finger the strings lightly, using only as much pressure as it takes to get a clear note. Don't strangle the guitar.

Don Firth