Get Resource Plan data without making a PSI call

I've found that retrieving project resource plan data (for all resources on the project team) takes around one minute when calling ReadResourcePlan via the PSI.  We'd like a way to retrieve that data without the overhead of the PSI call.  We've tried querying the Reporting database, and have found some differences.  For instance, ReadResourcePlan returns plan data, even if the resource plan is checked out / in a non-published state.  Is there a way to retrieve the same resource plan data returned by the PSI without making the ReadResourcePlan call?