We currently use the old crowd plugin wich did not require you to specify a group in its configuration.
The old plugin got all groups from crowd and then we could use the "Matrix-based security" under "Authorization" in Jenkins to set the permissions for the different groups.

We have three groups with access to Jenkins with different Authorization-schemes:
jenkins-administrators
jenkins-developers
jenkins-users

It would be great if this plugin could support this way of delegating the Authorization.