I lay-out a new set of holes on the opposite end of the tube. This time I used the mill. Worked pretty good. I then decided to countersink the holes. That did not work very good. The screws would not really seat very nice against the curved thin wall tubing. I then decided to cut off the end of the tube and drill my THIRD set of holes. Then came out okay. I will use pan head screws to mount the pitot tube to the mount