Electrical engineer to help size service conductors.

I'm working on a building with an existing 200Amp commercial panel in use and 2 - 60Amp residential Apartment panels. The 200A, 60A, and 60A are in an existing 3-gang meter. Within the building, there are 2 vacant units that the owner wants to lease out. with no meter. 1 unit will be a sandwich shop with a 200Amp panel and the other will be a barbershop with a 150Amps service. Load calculation for the 97Amp for the sandwich shop and 75Amp for Barbershop I sized up each for the future, so 200A for the sandwich shop and 150 for the barbershop. The service conductor will be in a 4" mast connecting to a power company-supplied splice box. Then on one side of the splice box will be connecting the existing 3 gang meter and on the other side, I will install a 2 gang meter. (this is happening because 5-6 gang meters are not available in my area) my question is how should I size the conductors? Here is what I came up with I don't think it is correct. Service mast conductors to splice box parallel 500Kcmil 3 gang 300A meter- use 350kcmil THHN 200A existing commercial 60A x 83%= 49.8A existing residential 60A x 83%= 49.8A existing residential New 2-350A gang meter- use 500Kcmil THHN 200A Commerical 150A Commerical Total disconnect amps= 650A. Do I need to parallel 500kcmil or do I use the load-calculated amp and size conductors to splice box? also do I use load calculation for 3 gang 350A meter or the load calculation is 175A? I assume I have to keep the existing 300A -2 gang mete at 350kcmil.