Air Conditioning - mastic over duct tape

My airconditioning ducting in the attic separated between a square duct to a round duct. The round duct forms around the square duct, but slipped off. I duct taped it back together, the two ends just reach each other, but then later read that mastic is the best way to seal it. I was wondering if I can put mastic (with a fiberglass mess tape) over the duct tape and seal it this way. Or do I have to remove the tape and start from scratch. :(

You can mastic over the duct tape and it will be just fine. They say to use a brush or putty knife to apply the mastic but do yourslef a favor and get a rubber glove and get a lil dirty and itll be much easier on you :)

Just make sure you cover the duct tape and some over on each side of the tape to connect the two pieces firmly.

Oh yea if you can zip some sheet metal screws into the duct work to secure it permanently before applying mastic, that would be the best way to ensure it won't come apart again. And while you're playing with mastic go ahead and hit any seams that haven't been hit :D