I am located in central Virginia where heat pumps are fairly common. We are, however, using a 90+ gas on the main floor and only using the heat pump upstairs. There is a fair amount of heat rise from the first to the second floor, so with our mild winters, it seems like it will work fine.
As for the supplies and return for the main floor, we will have supplies at each window but only one return. The floor plan is very open (no interior doors) so it should remain balanced. One possible location for the return is at one end of the house. My question is, with supplies all over and the return at one end instead of the middle, will the system be unbalanced?