Cartalyst Sentinel - Store additional data on persistences

I'm using Sentinel on a project and need to store additional data on the included persistences. The docs say this should be possible but do not explain what needs to be done to do so.

For now I have created a model and extended it with the proper EloquentPersistence class and with this the system works fine. I just can't find a way to add the additional attributes without altering the vendor files, which is obviously out of the question.

Is there a standardised way of doing this?

via Chebli Mohamed