Funnels are too thin and flimsey--not enough thickness ti give needed surface area. You ususally need to press down with all your might, and that usually tears up and shreds the duct tape. You usually have to re-tape it a couple times before you finally get it loose. I am a very persiwstent fellow and this method has EVENTUALLY worked for me every time. Sometimes gums up the edge of the glass though, but never seems to damage the coating, mysteriously enough. If it does, then paint thinner cleans it. Face it, when you had nothing for a lens to begin with, you might have to break a few eggs to make the omelet. Anybody's dumb idea can work, and I get lots of dumb ideas.