I'll tell you what I do-I will make certain the Patch Panel first fits the contour of the Body (Panel Lines, right curvature,etc.), then I will use a Clecos (or Sheetmetal Screws) to hold it in the proper place-I use a thin cut-off wheel to make a slit so I can insert my air-powered Hacksaw. Then, I will saw about 3-5" (or more), make certain the Sheetmetal is flush, Spot Weld and move on until the Panel is Attached. If I have planned correctly, the old Panel will just fall inside of the Car-make sense?