I bought a 1938 house, 850 sf. that was renovated with new central air & heating. However, I had problems with even heating through out the whole house. A licensed central air contractor installed a extra plano box with ducting & a larger return register & dampers. Adjustments will never be right. The purpose was to get more pressued air in the front rooms. I need more pressured air in the living & dining room. When adjusted this takes away from other room. He told me that I have oversized ducts. With the correct size ducts I will have more pressured air & less adjustments. Is this true?? How much should I pay to replace 5-6 ducts?? Will I get more pressured air with the right sized air ducts in ALL rooms with less adjustments? Need help?? Thanks!