Database modification

I'm integrating my forums' authentication with an external member database; it's working quite well thanks to the various posts, here, on the subject.

However, the external database allows up to 100 characters for the username, while the forums' Authors table permits only 25.

Off the top of your head (anyone), is there any danger in simply modifying the Authors table schema to make the username 100 chars rather than 25?

Thank you for any insight!
Don