I've been always wondering if our first floor system is short on return or not. Our service company never mentioned anything about the returns. I already know that the furnace and heat pump are over sized. There are a total of 17 supplies and only 7 returns. The returns are all 8 inch. The furnace is 90,000 BTU and the heat pump is 3.5 ton, which both are an overkill for 2200 sq. ft. in Atlanta, GA. If we really are short on return, it's impossible to add any more because expensive dry wall work will have to be done since the basement is finished and the ductwork is above the basement ceiling. Do you think the system is short on return? I apologize if I didn't include enough information. Thank you in advance for any input.