I just recently replaced a 4 ton system with a 5 ton system. Most of the duct work in the back of the house was redone and the unit performs very well in that section of the house. The original duct work in the rest of the house was tied into and performs sub par by my standards. The installer said even if he reworked all the ducts in the rest of the house the performance would probably not be any better. He said it’s sized correctly but it’s just a very long run! He did suggest multizone from the start but we don’t plan on staying in the house very much longer so he didn’t even price that out. Is there anything I can do to improve the performance to the other ducts? Is it possible to retrofit mutlizone now?