I have hesitated to say this, but what the heck! What I have done in the past with a complicated piece like this is to take my steel and mark the lines I need to bend along on the backside. I then take my die grinder with a thin wheel, and I "scribe" it. As it thins the metal out along where it needs to be bent, it makes shaping the curves much easier. Then I set my welder down low and weld along the inside where the scribe is to add strength. It's probably not the best way to do it, but it's strong, makes life alot simpler for a novice, and certainly gets the job done.

I like to cut out the original piece to good metal, take the piece you cut out and flatten it out to use as a pattern for the new patch, cut the new patch, and bend to the contours of the existing metal.

It takes practice, practice, practice!

I haven't had much trouble cutting and forming patch panels for a perfect fit, but I've had a terrible time preventing major warping. I'll slowly do ~20 to 50 little tacks, and then slowly do stich welds from there, but with a TIG, I just can't sem to keep the part from getting too hot.

Molloy, try taking a water-soaked rag and cool down the area after a couple of welds.

I had the same problem until I started doing this.

I use air to cool down the welds. Seems to "shock" it less...but maybe that's just me...

Jerry, Make sure when you trim out he rust, to get to good metal. Rust does not weld well.
My 72 Charger had the rear body lines wiped out in bondo. I knocked all of that out and made sheetmetal pieces in a bender to put the body lines back in. The edges by the wheel well radius, I made cuts every 1/2 in. or so and genlty bend them in to fit the radius. after wire feed welding ,it ground down pretty smooth.