1. Lay tape over the area to be patched. Use a sharpie if needed to assist in defining what needs to be made to fit the hole.
2. Use the utility knife to cut the tape to fit. The portions in pen above and below this piece are OK if they’re close, so I’m just going to wing it. The tape is wider than the channel elsewhere, so it fits just fine. Tape can be layered overlapping to create a wider tape template.
3. Pull tape off of the channel.

   (1)

   (2)

   (3)

4. Put tape onto the sheet of steel so that the patch panel can be cut out. Notice that the “DS Patch Panel” is curved. That one came out perfect, and the flat sheet just needed to be gently curved to fit the curve of the channel on the top.
5. Use the nibbler to do a rough cut. The nibbler has no hacksaw teeth and moves through the steel quickly. It is not precise enough to get within more than a few millimeters of the desired edge. It cuts in a piston-like motion that acts not unlike a paper hole punch, just for sheet metal. Beware that it spits out the crescent-shaped nibbled cuttings out the front, so eyeglasses are important. It’s also really important to point the tool at a specific area to keep the shavings shooting into a place that they can be effectively cleaned up. The first time, I blew them all over the place like sawdust, and they’re sharp little buggers that embed themselves into the soles of your shoe if you step on them. I had to pick 40 of them out of my boots and now try to contain the shavings……
6. Panel is cut out. Note that the black pen lines are the desired shape, and I’m not there yet.

   (4)

   (5)

   (6)

7. Use the grinder to grind down the edge to the pen. I did half my pieces like this until I tried the body saw. It’s essentially a jigsaw/mini-sawzall with a reciprocating hacksaw blade. It is incredibly precise and buzzes right along whatever line you need, providing there are no sharp turns.
8. The result – The piece is trimmed to the shape that I think that it needs to be using a bench grinder for the finer trimming.
9. Fit the panel up to the car. You can always trim more as needed, so go in rough and shape to fit was my method.

   (7)

   (8)

   (9)

10. You can see where the tape is on the panel. That’s the portion that will be visible. The top and bottom will be bent a bit to allow the top and bottom to submerge under the remaining body metal. This is a very crude flange. To weld, I’ll drill through the car’s metal, leaving a hole that the flange of the patch metal will be visible through. I’ll bend the flange metal up so that it’s flush with the hole in the upper metal, stick the welder in there, and weld through the hole so that the walls of the hole fuse to the flange underneath.
11. That little nib on the end is preventing me from sliding the panel down through the hole far enough to allow the top edge to fit under the lip of the top edge. I used the air-powered body saw ($19 at harbor freight and worth it!) to cut this. The body saw is like a sawz-all but it has hacksaw blades instead. Get extra blades if you get one. The local hardware store didn’t have them.

    I’ll weld the two pieces that I cut apart back together later.

12. Piece now fits.

    (10)

    (11)

    (12)

13. Bend the piece around a little so that it is sitting in the hole touching the top and bottom edges. I plan to weld along the edges too, so this is perfect and the tape is removed and I go onto the next piece and repeat.

    (13)

Here's the result of installing the patch panels: