it never hurts to even get a third or fourth expert A/C person's opinion. how old are your ducts ...maybe time to have them replaced and redone correctly so there will be no leaks ....usually condensation forms when the cold air hits humid warm surfaces i.e. the warm humid ducts exterior surfaces. I have always been told that you can never over ventilate your attic in the hot summer months. get additional opinions and suggestions/estimates for repair. good luck. LJ