Yes Rick, I think you are definitely on to something regarding the neck shaving. My guitars all have 1 11/16" widths at the nut, which is considered "slim", but they have "soft V" necks, of which the extra "beef" can make it challenging to wrap around with the thumb, and nail both the 5th and 6th strings together.

Perhaps I should just seek out an early 40s herringbone D-28 and have a shaved Bigsby neck grafted onto it?