RJVB;

Your reference to a resonator with nylon strings was new to me--I was wondering more about traditional flat-topped classical guitars.

The sound hole shape is important on the electric/acoustic being formulated on this forum. I want enough acoustic for song writing and play with small acoustic groups.

Casual;

The research paper suggests that the best performing part of a violin sound hole is the edge where sound pressure is the highest. Do you suppose the paper is talking about the edge of the hole or the edge of the instrument? If the reference is the edge of the instrument then the off-set sound hole makes a lot of sense.