Unfortunately the ideal place for the jam room in this house contains a lot of the hvac. I'm putting all ducts behind sealed, caulked, well constructed mdf at least, with plenty of duct liner and baffles and acoustic caulk etc. I had to move the whole supply plenum over about 4 feet so I made some turning vanes to keep things efficient through the necessary 90 degree turns.

I was able to do the return stuff without any sharp turns but it sure is bulkier. There is a corner in the room that is an unmovable object, but I was able to use the extra space to create a very large baffly thing to quiet the air moving out of the jam room into the hvac system.

EVERYTHING will flow better, and everything I've touched has massively improved fire safety.