What I have done and it does work well. But try on scrap line. Get the flare to bulb the line in the first step. Then with it clamped into the tool, before using the cone to fold the line inward take a smooth headed ball pein hammer and tap the bulbed part flat working the metal inward. You dont have to really smash the **** out of it, just work it down flat and towards the center of the hole. Then put the cone part on to drive it inward to create the double flare. This works great this way. Try it.