23 seer mini spit upstairs, older 5 ton 13 seer down stairs, upstairs 600 sq ft with balcony looking down stairs.12/12 ceiling. The upstair mini split will maintain 65 even with the door to balcony and stairs open with cool air coming down. with down stairs unit set 75 i woke up to 72 in down stairs and the cooling had be coming from upstairs mini that was set on 68. What is the best way to utilize for energy and cooling