the thermostat that calls for heat is best thought of as an on-off
switch where the demand for heat is requested. could the factor of the
house's heat loss might be better handled with a variable speed blower?
remembering the comfort of your home in winter requires a balance of
temperature and humidity and sufficient oxygen from air changes.
if you blow the heat out of the plenum too fast into the house you will
not enjoy even heating of a close temperature differential of one
degree.
if you blow it out too slow the house will drop below the desired
temperature. get a digital thermometer with high low memory and monitor
the temperature at the thermostat to see how your range varies, and
determine a course of action to zone your home so no room gets excess
heat.