S-F thanks for your help! So, my plan was "mastic the hell"
outta the metal duct work. My supply tubes that distribute the air are pretty good. I had got up there a few yrs. ago and zip-tied everything back together, but I got spots where the outter plastic wrap has just fallen off.
Can I just take that FSK stuff and wrap it in those spots where the plastic came off, and on a few of the places where it splits?