I had some back luck hiring a couple PMPs when I ran a consulting division. They're very much old-school in their methods. Big Gantt charts, PERT, waterfall, etc. Didn't match at all with my move towards a more agile approach and we had conflicts.

The best way I found to manage bigger projects was to get technical PMs who still coded, and break down the management into a few sub-teams, each of which could still work in an agile fashion.