Cleanest way to cut the holes would be to punch them w/one of these, ~$25USD:
from
here.
Sort of like a heavy duty paper punch. You drill a small hole, ~1/4 in. dia.
One piece of the punch goes on either side of the panel.
Then draw the two pieces of the punch together on the threaded shaft.
Bingo! Very clean hole that needs little/no clean-up.
