They got it right, you have to use really strong thread. Another way to make the foam thinner and stick is to shave your foam sheet in half. These will make it half the size in thickness. Do this with a few colors and then glue one color on top of the other. Use a natural color and a bright color on your fly, with the natural color on the bottom and the bright color on top for visiblity. Now how you have to do is cut to shape and tie onto hook. Another hint for making an effective chernobyl always put tons of rubber legs on the fly. The rubber legs not only help give the action to the fly which makes so deadly, but they help it float by relasing water tension.