I figured I needed a little practice installing side ports before I cut a hole in one of the tenors building. I had a scrap of curved maple to practice on and began by drilling holes around my scribed hole with a dremel drill bit.
Here is the rough hole
Now it gets tricky. sand the edges down to the very edge of the pencil mark but no further. I am using a dremel to do this, and here is the completed hole. lets see if it fits.