I just did a 200A service in a small 2-family, both panels are fed via 100A breaker from the meter/main.
The first flr panel is 42 cir 200A MLO, due to the fact that the owner has almost every device on it's own circuit.
I could, by code, place another 42 cir pan next to the first, the premis being the load demand & diversity, NOT the number of circuit spaces vs. service size.
