As Jerry says: Sometimes it does not matter where you buy the patch panel, it does not fit exactly. It's either the truck or the panel or both at fault. You can always make it work. It's a common issue.
Also, what I have found is best is little dots of mig connected together. Slightly stacked. (3/16-1/4 dia.) Like Jerry said, do them several inches apart. This is where us novices should take note. We don't understand how important it is to make them way, way apart, and even then, wait until the recent spot is cool. Jerry can do it, we can't. We only have a few panels to do on one truck. Got plenty of time. Us novices are in a hurry to keep welding to get it all stitched. If you don't slow down and wait for each weld to cool you will warp the panel and then you are done. You are in BIG trouble. It may all have to be cut out. If it takes hours to do it slow, so what? Small pieces and pieces with bends are more forgiving than a big flat panel regarding warpage. Don't spend all that time trimming, aligning, clamping just to warp the thing. SLOW and easy. Use the flattened end of a copper pipe behind the weld if there is access. Bend it to shape up behind. Weld won't stick to it. It helps to fill a blowout and etc.
75/25 gas, Argon/Co2 is better for thin metal/body work. Most mig'ers use 75/25. %100 co2 is too hot for thin, unless you are experienced. It's all done with butt joints and they should be butt tight! Credit card gap or thinner. If you use butt clamps, grind the blade down.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn