
   My rule of thumb is "Don't give rides to people that wear
a bigger helmet than you", unless your taste runs that way,
or they are family.friends.
Gee,  reminds me of a *dancer* in Hull, just over the river 
from Ottowa, that I saw a few years ago, for her I would a
bought a bigger helmet (or even her own bike) or anything 
else she wanted ;->