My basic setup looks like this - Contexts are defined traditionally within the Categories area of Highrise:
To further break down items I have also created Cases for all my major areas of focus. These include Projects, Teams, Committees, and Focus Areas:
If you are familar with the basic GTD methodology this should make sense. If not I highly suggest checking out the book: Getting Things Done: The Art of Stress-Free Productivity
Adding tasks under Contacts will continue to serve their purpose for niche items but over time I found that my deliverable to individual contact was more than likely a deliverable related to a larger project or organizational initiative.