To make this work, I needed a new routing template for the chambers. I posted this in my Maple Thinline thread but since I was taling pics anyway...
Starting with a standard template, I drew a center line, measured out 2" either side and, then drew out the curved lines for the chambers. I used a couple of spacers...one to ride along the edge of the template and one to space the pencil out to the distance I wanted. Then I just traced the template like you would with a router.
I added to lines that are at the center point of my Forstner bit making it easier to stick and go while drilling.
This kind of drilling makes a huge mess so I hung my dust collector hose overhead so I could grab it and keep things cleared off.
All drilled out and ready for filing.
I figured out that I was putting too much pressure on the fragile template while filing with it on it's edge, so I layed it flat and hung a small portion over the edge of the bench and clamped in place, letting the bench support most of the template as I filed.