Hoping to get some pointers on how to weld this hole

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So I'm working on a '78 Fiat 124 Spider, and as usual finding previous damage under the paint.  In this case the rear of the fender was hit, looks like they hammered it out and sanded it down, and went through the metal.  I have been looking at several options, including epoxy putty (the width if about 1/8" at the widest), but welding is my preferred solution.  Thing is I am worried about some warping in this very visible area.  The whole area in about 2.5" in diameter where the metal was worked.The picture shows the hole, but the thing to remember is the metal is super thin all around the hold due to the sanding.  So I'd like some pointers on how to handle this, and here are my questions.1. Should I use a copper spoon and slowly tack this hole up and grind it down and be done with it?  I think when I start to weld I will be chasing a hole till I get to thicker metal?2. Should I cut away some of the really thin stuff and slowly build up the gap using a copper spoon on the back side, and clean up afterwards?3. I have a fender off another car; should I cut out the whole area (an inch in all directions) and weld in a whole new piece?4. Should I cut along the crease and weld in new metal along the crease and new metal just on the outside of the crease?Here is a picture of the hole in the panel.https://www.flickr.com/photos/69277887@N00/16249276050/I've welded lots of flat areas on body panels and use the round robin tack method to good results.  I am using a 120v Mig and .023 wire.  But no matter what, eventually I will get warping from time to time, and this being such a visible spot I am trying to attack it the right way first so I can minimize damage control later.Thanks all!
Reply:I'm just an amateur, but I'd most likely cut it out and replace the area with healthy metal. Preferably O/A or TIG welded so the welds are soft and some careful panel beating can be done to fix the unavoidable warping due to the welds shrinking as they cool down. I recommend you ask the guys at the Allmetalshaping and Metalmeet forums too, there are some really experienced sheetmetal shaping guys there. (Throw a towel over your keyboard first, you WILL be drooling when you see some of their projects.)http://www.metalmeet.com/forum/index.phphttp://www.allmetalshaping.com/
Reply:I vote 3.
Reply:trying to weld on tin foil is not something you want on an auto body.....cut the bad area out and insert a good piece and blend the weld in   Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:I'm with BC's idea,Also since your're LUCKY enough to have a similar good panel close by you and the bad area is small , you can make the replacement patch from copying the area from the 2nd panel for your repair without damaging the 2nd panel.If you make an error with the patch, you still have a 2nd panel to make a 2nd attempt with a patch copy.And if you can weld with OA, and have access to a small torch outfit like the little torch(smiths) you can make two patch copy repair panels, choose the one with the worst fitup/ contour, tack it up to scrap pieces of your patch material and to a test run to dial in your torch tips/ gas flow settings BEFORE going on the actual fender repair… for piece of mind not to screw upJust my 2 cents
Reply:Yeah, I think the consensus it pretty spot on here.  I'm gonna weld in new material.  And Maxstar, that's a good idea fabing up a new piece using the good fender as a template.  Then I can screw and just start over...  Thanks all
Reply:That area is pretty rigid having that body line there but you will still have some shrinkage. When cutting your patch panel leave a gap about the thickness of the mig wire all the way around. Using the copper spoon you'll be able to turn up the heat a little and you'll get full penetration with the patch to existing panel being an open root. Grind down your welds and get out the hammer and dolly too stretch the areas that were shrunken by the heat from the welds.
Reply:Originally Posted by Sharon NeedlesThat area is pretty rigid having that body line there but you will still have some shrinkage. When cutting your patch panel leave a gap about the thickness of the mig wire all the way around. Using the copper spoon you'll be able to turn up the heat a little and you'll get full penetration with the patch to existing panel being an open root. Grind down your welds and get out the hammer and dolly too stretch the areas that were shrunken by the heat from the welds.