CommunityEngine

Thanks for the info and pointing me to the Google Group.

Like you said, as long as you don't remove existing columns from User, you should be fine (provided future migrations don't conflict with what you add, which is unlikely). You don't need to generate a plugin migration, you just generate a normal migration and alter the users table.

Also, you're better off posting questions to the Google Goup (more likely to get answered there).