Go with Fat Charlie's method. Use a hole saw that will take out the most material easily then get in there with a diegrinder bit on the Dremel. Don't waste your time using cutting discs, just start chunking out metal and move slow so your don't "color outside the lines"
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-Mike
2007 Ford Focus ZX5 - 91k - SGII, pending upper and lower grill bocks - auto trans
1987 Monte Carlo SS - 5.3/4L80E swap - 13.67 @ 106
2007 Ford Focus Estate - 230k - 33mpg - Retired 4/2018
1995 Saturn SL2 - 256K miles - 44mpg - Retired 9/2014
Cost to Operate Spreadsheet for "The New Focus"