If you have one POC that is feeding the entire system, then that is all you really need to focus on. The main POC is going to hold all of what is available. The sub meters at each building is more of another piece of equipment that should be called out, but not what immediately dictates what the demands of what each building will be sized to.
You have a few options here:
1- Keep the main POC as the single source- Size the entire system with multiple valves at a time, even picking which valves run together for worst case scenario. You could even integrate Flow Zones in and around each of the buildings to keep the flows a bit lower and the main trunk of mainline feeding all buildings a bit higher.
2-Add 9 Points of Connection to your Source Data and input the exact available pressure and flow for each. Place each POC where they would essentially be tied into the main mainline, and size each POC to get the demands of each building.
If you are required to the size the mainline back to the Original POC, you can take the Critical Analysis of each POC, place Caps at each of the 9 POC's and input the demands of each, and pipe the mainline from Caps back to the original POC.
Below are a few links to items referenced above. We are also happy to chat more if you would like to send in a technical support ticket.
Power Tip: Put A Cap On It
Adding & Placing Auxiliary Equipment