Im currently building 2 koa ukuleles, one small and one not-so-small. The small one is very much like a 40's Martin soprano. The bigger one has a tenor scale, but the body is between a concert and tenor in size. Illustrated in the pictures are rosettes being cut, installed and glued as well as the sound hole being cut out. I made the little jig to hold the tops using a 9/32" piece of tubing cemented into a piece of MDF. This "locks" the top into the jig and keeps the cutter head on center. I milled the cutter on one side down to the width of my rosette and sharpened the cutter like you would a chisel. The other side of the cutter is then used to cut out the sound hole.