Hate chime in late but had make sure brain was in gear before opening mouth.
IF 5/16 course thread you can drill with a 5/16 bit and re-tap at 9mm-1.25. Make sure to use rubbing alcohol on the drill and tap for smoother finish and to prevent the tap from sticking in the aluminum. Of course assumes that you can drill straight with no wobble and the same when tapping. Plus you would need open up the hole(s) in the head slightly.
