I have drilled and glued mine in tonight and used metric drills, only because I can't think who borrowed my imperial drills.
NEVER A LENDER OR BORROWER BE, INIT? A bloody good and true saying, Why can't I live by it?
10mm for the bottom tube and 11.5mm for the top, the bottom surprisingly fits snug and the top needed a bit of a push to get it in.
Tomorrow will discover how they fair when spinning init?