Matrix Managers - Access to Performance & Goals

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My customer has a requirement for Off-Hierarchy Managers to be able to review goals/carry out check-ins for somebody they are working with e.g. Project Manager etc.  The only way I am aware of we could make this work is to use Matrix Managers. 

Does anybody use this, and if so could you help with the following questions?

1. If we add someone as a matrix manager, I am assuming they can do everything for that report that is available from our custom Line Manager role i.e. Employment Info, Absences,  Transfer etc? and that we would need to strip the performance functionality from our Line Manager role and have a custom Performance Manager role?