I am about to add onto my house and am putting in new trusses. The problem is the air supply plenum will need to be moved up about 6" from the air handler (the trusses just happen to start where the air handler meets the supply air plenum). I suppose I could move the entire air handler up but this would involve changing the hot water supply and drain piping. Is there such a thing as a flexible rectangular boot (24" x 18") which will allow me to adjust the plenum to where I need it? If so, where can I find this? Thanks in advance.