I hope you guys can offer some words of wisdom. I am in the middle of a down-to-the-studs remodel - doing all the work myself. The house is a rancher with a 2/3 basement and 1/3 crawlspace. The system currently has (8) 6" round ducts coming off a square trunk. 6 exit up into living space from the basement and 2 exit up into the living space from the crawlspace. No vents in the basement. The system is now stripped down to the trunk. My main problem is that I need to move 2 of the ducts a few feet from the edge of the basement to the other side of a block wall into the crawlspace (to exit into the living space above). The trunk going through the block wall is not big enough to support the additional (2) 6" ducts. So I think I need to extend the trunk that is big enough to support (4) ducts by a few feet to get it through the block wall. Is this a straight-forward procedure? Can an HVAC supply place set me up with the materials? It seems like keeping the number and size of the ducts the same really helps me stay out of anything too complicated.