This is a story familiar to most luthiers, a mistake or accident forces you to change direction and make some adjustments.
New member and 2025 Acoustic Building Class student Stephen Freeman encountered a set up problem with one of our rosette circle router jigs that caused the rosette ring that he routed to be slightly ragged and also slightly eccentric on his OM top.
Adding inner and outer rings was going to be impossible without a major revamp of some type, and was also going to put him a week behind the rest of the class when we resumed next weekend if he had to wait for new materials to arrive from Stewmac.
First we determined the issue that had caused the cutter to be unstable and fixed that.
Then we decided to re-rout the orginal rosette channel being careful to remove all of the the old eccentric hole and all of the surface of the aready installed rosette..
Larry had some jumbo sized Hosco dreadnought rosettes in his stash and after a brief consultation, a new way forward was charted.
We warmed the oversized rosette with a heat gun to rebend it to reduce its radius, and trimmed the ends to allow it to fit the smaller OM sized soundhole more closely.
Since the Hosco Herringbone rosette was only 1.5 mm thick (about half that of the old Gurian rosette) this necessitated leaving about 1/2 the thickness of the old rosette in the new channel to act as a shelf under the new rosette..
Stephen then carefully routed the new channel to acommodate all 5 of the elements of his previous 3 ring herringbone rosette scheme into on larger single rosette. Combining two layers of BWBWB .050 purfling with two layrs of grey Abablone zip-flex and a Herringbone rosette was a little fiddly and required 4 hands but with a little help from Larry the rosette fell into place and a really nice result was achieved.
Congratulations on a well conceived, and executed, fix to a thorny dilemma.