Running multiple User Profile Service Applications -- recommendations, pitfalls, etc.

I have a farm with one WFE, one APP, and one SQL server. The User Profile Service runs on both WFE and APP, the User Profile Sync Service is on the APP server. There is a single User Profile service application running that pulls from 4 different AD import sources: two in the US, one in London, and one in Mexico.

There is a nightly incremental synch.

There is an issue where the London users need the synch to occur hourly.

There are some complexities with one of the US sources in that would make it difficult to run the current User Profile service hourly, plus there is a performance concern.

I'm interested in possibly creating a second User Profile Service Application that reads only from London and runs hourly.

Beyond creating the User Profile service and scheduling hourly, what should I be concerned about?

• Will I need to (re)create new Audiences based on those from the original User Profile Service App? Run them immediately after User Profiles? Will there be an interruption in access during that gap?
• Recreate custom User Properties?
• Recreate any Forefront modifications?
• New Profile/Sync/Social DBs?
• etc?

Thanks,

Scott