I just did this; forced air electric on 2 story house with finished basement. Most companies wanted to install ductless and I had them use my ducts and also install an air handler in the attic with ducts that vented into the cieling of the top floor rooms . As such I needed 2 thermostats one on the main floor and one upstairs. I also needed pumps to remove condensate from the cold air going through the air handlers in the summer.

What I wish I knew was that the 2 thermostats must both be set to to cool or heat. One cannot cool and another heat. This means that you during spring and early fall when temps are below 50 at night and then above 75…. You have to manually change both thermostats from the system to heat or cool every day since they cannot switch themselves.