Besides weight, I know for a fact they wont hold up to fuel, so you cant put them in any places that gets sprayed. Unless its electrics you are talking about, Also when elctrical tape gets warm it tends to get gooey and slide or peel off. I wouldnt recomend it for covering unless it was a quick patch. Not sure about the duct tape issue as far as holding in those elements it should stand up. But again the fuel issue neither one is fuel proof.