I purchased the new swingarms that require the frame to be drilled and went down to the local hardware store, they only have 10.3 mm bits, does that little difference matter?
I would not go with 10.3 as this will create a play and eventually weaken the structure.
10mm is in fact too much play so I went with 9,5. It is so tight that you need to thread the bolt in slightly. Alu is very soft so it is very easy to just screw it in.
So no more than 10mm even better if it is 9,5-9,7mm