Duct tape is a great idea. I’ve also been using a lot of gorilla tape for temporary repairs around the house and yard.
Rob, I believe Sapote mentioned to wait until the mango starts to fruit before grafting because the original poster is in SoCal and grafting young seedlings in our climate with mature scions will likely cause the grafted tree to flower that winter and every winter there after. Flowering in SoCal often encompasses a period of 6 months starting around October or November when our temperatures start getting significantly colder.
Simon