Minisplits upstairs might be a good idea. Also, anything to reduce the stack effect. You might have air leaks pulling heat upwards all day. Our house is old and

Minisplits upstairs might be a good idea. Also, anything to reduce the stack effect. You might have air leaks pulling heat upwards all day. Our house is old and retrofitted, so the return air upstairs is inadequate but closing the downstairs vents makes a huge difference in the summer, since old air sinks.