I used wheels with to big a centre bore for ages with no vibrations or damage. Micras aren't hubcentric. I know this cos now I have a hunbcentric car and the wheels are a ####### to get off.
I have seen flat faced nuts but only on a 4x4
All the strength is in the bolts, otherwise the wheels would snap off everytime you did a handbrake turn, no offence ant but sometimes even the experts don't know what they're talking about. You may have a problem with hubcentric cars which take weight on the hub