Eh I don't know. If anything maybe a metric m3.5 screw? I know you can use those with a 6-32 thread and they hold okay. Depending on your manufacturing methods maybe expand the hole by 0.05 for some tolerance. Would leave a 0.9mm metal gap between holes. Laser cutter can probably do that with reasonable precision.
Personally, I would try a test on a small panel. The screw might go in a little tight and rub the hole down, aluminum is soft
Another concern my friend brought up is the panel heating up during laser cutting and thus having it's structural integrity compromised...
Anyways, I think it's worth a shot, for sure. Probably won't use it immediately though since I want to use normal screws etc.
Thanks for the insight on screw tolerances and it being quite loose on the fan, that's interesting... two levels of offset! screw to panel and screw to fan