We are considering moving into our 337RLS full time in a few years, and would likely live in the Casa Grande area. Temps during the summer routinely get above 100, and sometimes up to 115. I will still have a few more years of work before I can retire, so we don't have the option of moving north during the summer. We are planning to install the second AC unit prior to then, but are concerned whether even two units can keep us cool in that heat. Has anyone had any experience with this type of heat in their 5er? Also, does the second unit tie into the duct-work like the main unit?