Hole saw works best, deburr with a Burr-Kwik sheet metal deburring tool. SOUND is the biggest compromise in airboxes. Intake noise can be louder than exhaust.
I'm with the "keep it intact as designed" group.
Too much is just barely enough.....
2007 Tiger 1050
2005 Royal Star Tour DeLuxe
1973 Yamaha TX750 1984 Yamaha RZ350
1974 Norton 850 Commando Roadster