While we at Don Rickert Design and the Adventurous Muse (www.AdventurousMuseStore.com) have experimented with fretted instruments, and will continue to do so, we have a customer for whom we are doing a special version of a Travel Master Pochette (Travel Fiddle / Violin) with tied frets like a Renaissance Fiddle. The use of frets is pretty much what distinguished the Rennaisance Fiddle from the Renaissance Vielle, an updated (from the the Middle Ages) version of the Vielle that was pretty much like a modern fiddle in many ways.
Instead of gut, we will be using monofilament (15 lb fishing line), using one of several methods for tying what is called a "fret knot". Tied on frets allow the player to adjust the intonation (by moving the frets) depending on their bowing style, bridge height and so forth, variables that are far more important on violins than guitars for good intonation.
We'll let you know how it goes. Another advantage of tied frets is that they can be cut off if it doesn't work out.
If it DOES work out, you can be sure that we will be doing a story about it.
Visit our online store (www.AdventurousMuseStore.com)...yes, that was a shameless plug.