Let me start off with a brief overview of the house. It is a 2 story with seperate split systems for upstairs and downstairs. Roof is a hip style roof. Upstairs has approximately 800 sq ft, and the house is practically square in shape. Currently the air handler and all duct work is in the attic. There are 8 registers in the ceiling with 6" metal pipe to each from the existing plenum which is at the top of the shaft I will discuss in a second. The upstairs unit recently went out. I have talked to 2 different companies that have told me two seperate things. I expressed interest in not using a split system for different reasons, but that is beside the point, but instead would like to go with a self contained package unit located outside. Approximately 8-10 feet from the outside perimeter of the house, I have a unused dead space shaft approximately 3' x 4' that runs all the way up through the house. Downstairs it is just a closet, and upstairs it is sealed off. Anyway, I expressed interest in going with the packaged unit, but wasn't sure if that was a possibility due to supply and return issues. One contractor told me that it would be tough and wouldn't really discuss any further. The other contractor told me that it could be done rather simply. He said that for the supply and return, he could run the 14" round metal duct under the crawl space approximately 8-10' and then elbow up vertically and run up through this shaft all the way to the attic. He could tie the return into the existing 12 x 20 return grill that is located on the wall of this shaft upstairs, and run the supply side on up to the plenum. He said that he would take out the entire trunk duct that is existing in the attic except for the plenum, and would run the supply lines to each register out of this. He called it a radial duct system or something like that. Does this sound right? I would really like to do this if it is right, but I once owned a 2 story home, and the upstairs system was a split system and it never worked right. Heat, high humidity, etc. I just don't want that again. I really want a outside unit. I would appreciate any thoughts you guy's have on this.