Here is how I cut the rosettes and channel for an eccentric rosette
Basicly The top fits over and slides of the bottom board
The top has ears along the side so the slide only happens in a perfectly strait line
The rosette material is centered and taped at the top pivot
The top is taped to cut the rosette channel at the bottom pivot.
Top and rosette require oversized centering holes so the shift can be made.
Notice the blocks and clamp at the bottom.
The zero position is with this unit up against the bottom block (block is attached to the bottom of the unit only
After doing the inner cut of both the rosette and the top the shift is made on the board.
A shift of only 2.5 to 4 mm makes a very pleasing rosette
Then the outer cut of both the rosette and top are made
Then you have to go back and carefully wicky wonk out the rosette channel in the top.
Your rosette is done so take it to the drum sander and sand off the backing but leave just a very very little on and clean by hand.
Since you used a .032 router bit you can simply drop in a .030 BWB purfling strip on the inner and outer edge of the rosette and you are golden
Drop that rosette in with the inner and outer purfling and set with CA (but be sure you only use a very little as if it leaks through and glues you work to the board you will be hateing on me
Return your unit to the zero position (up against the block) reset your router to cut out the inner circle (you could have done this before dropping in the rosette but depending on narrow you make that piece between the rosette and soundhole it can get a little weak
Durning these processes tape your top to the unit well and never take it off till you have made all your cuts. You will not be able to realign due to the fact the top has a half inch hole or there abouts.
Make sure you use a sqeeze clamp to secure the unit in each position. You can only return to the zero point up and down.
Your unit shoud have zero play side to side. Make fit nicely over the bottom.
I used 1/2" Iron wood for the blocks that support the pivot points which are 1/8" Drill bit shafts
The square holes in the top of the unit are 6 mm or so longer and just a little wider than the blocks (having a little play there won't matter but you need enough to make the shift)
Use this unit and method for non eccentric (standard rosettes) just don't make the shift. The great advantage of this method is you are cutting the rosette at the same time you are routing the channel in the top so you don't need to reset your router pivot or depth except for the inner and outer cut.