I am building guitar for a guitarist who only uses gut strings.  He has already told me that if the guitar doesn’t “work” with gut he doesn’t want it.  I wouldn’t normally accept to do something like this but this sounded like a fun challenge.  The truth is he usually only plays on historic instruments so I might learn that he doesn’t play this one much even if he finds it compatible with gut strings.  This first photo shows a few of the changes I have made in this guitar with the intention that it sound better with gut strings.  Torres didn’t scallop his braces but I did so on these.  Torres linings had a triangular shape, even slightly convex in their profile.  On these I made a concave face to reduce mass without losing any width because the purfling on this model is very wide and needs support.  Other changes I made were to use very lightweight wood all round, a top as thin as I dared and to use less doming than the original.  I had considered using spaced peones but I severely dislike the small spaces left in between that break up the evenness of the interior.  I am also looking for a soft fretwire to use hoping that the strings will last longer.  This photo shows something that I got from another guitarmaker when I was restoring a guitar from 1900.  Intonation will also be an issue with the gut strings.  I hope to do some experimentation to see if gut needs the same compensation as nylon.