For 15 years, Jeff Senn has been building, repairing, and modifying guitars for Nashville’s touring and studio elite. His double-cutaway Fullerton and single-cut Pomona are in the hands of guys like Tom Bukovac, Jedd Hughes, Rob McNelly, John Fogerty, Steve Wariner, Bruce Springsteen, and Audley Freed After building tribute guitars, Senn recently returned to his …