Reinhard,
P-Mail me and I'll be very happy to give you the permanent solution for
the loose mirror's.
They will remain tight forever.
No crazy sanding.
No crazy filing
No crazy super glue.
I found the answer in the archives and it works very good.
Tighter than a knot in a wet pine board.
My boy almost knocked himself silly when he bonked his head on the
mirror as he rode a bit too close on his bicycle.
The mirror didn't budge.
He did. :)

RC