Change {authmap}.authname type from varchar_ascii to varchar

This does not change the type of the field, but rather the length?
Is there a specific reason the authname should be longer? i.e. compared to the Drupal username field (60 chars), the authname length of 128 is already double.
I don't mind increasing the length, but this would need some more testing with real installations, to make sure this does not break things, as changing database tables always feels a bit risky to me.