I would like to know how many F-Secure clients can you connect to a Policy Manager Proxy? I understand it's 500 concurrent connections but what is the recommended number of clients that should be pointed to one policy manager proxy?
PMP is only acting as a proxy, the number of clients is not limited. But you certainly should not make 20.000 Host poll every 5 Mins to the PMP. furtehrmore PMP throttles the number of concurrent connections and the number that can be serverd depends on the size of the updates (thus the time each client needs to download) the number of updates per day, your bandwidth aso.
I'd recommend to additionally activate neighborcast between the hosts, so that they can share the databases directly.