WHAT IF I WANT TO HEAT MORE THAN THE HEATBOARD KITS WILL ALLOW?

The Mysa thermostats will only handle a maximum of 150 square feet for 120V and 300 square feet for 240V. I suggest splitting the areas into zones with a separate thermostat for each area. The Mysa App will allow you to control all of the zones together from the convenience of your smart phone.