Talk about cutting her close!
That light grey half moon shape in the inlet side is as close as I could get with the drill before encountering the port window. I estimate it to be about 1 mm, so good enough for me.
My matching job on the exhaust side. Used a die grinder and like always, went slow. It's matched up pretty good, it was horrible mis-match before and I didn't realize it. Definitely should see a marked improvement.