I used both those patch panels and I didn't have a lot of trouble at all. The inner cowl panel comes with the incorrect curve at the bottom. I flattened the flange, and modified the curve to fit front and back. Because the curve at the front is quite different from the back shape, the metal has to be stretched. I did the stretching at the back as there is more than one radius involved. You can do that by holding the piece at a slight angle to the bench and striking it downward with a body hammer that has a very slight curve. I practiced on a piece of 20 gauge and found that I could make all kinds of complex shapes.
The inner to outer will not fit exactly every time. So, just bend the inner face at an angle to go further in than you want and make another bend to bring it back at the correct angle.
