After drilling the required 1 inch hole last night for my Andair fuel selector, I did a test fitting and found that the fillet radius on this boss was interfering with the corner around the bottom surface of the hole.

After a bit of work with a file, I had a nice matching radius.

This isn't the recommended technique for match drilling the mounting holes, but I figured if I wrapped the whole thing in tape I could prevent any shavings from getting inside the valve and it was just a lot easier to drill the three flanges this way. I used a #11 drill bit.

I also decided to drill the 3/4 inch hole for the manual trim knob. Might as well get 'er done while it's out of the plane.