Based on my experience with doing the exact thing you're attempting, I'd recommend the dot method, planishing each dot as you go. Flat panels are especially sensitive to shrinkage at the weld joint and the planishing helps keep things flat. I predict that you'll need to do some shrinking to get the panel flat again after you complete the patch, even with the dot method. I wouldn't try to run beads, as that panel will likely become warped beyond salvage.
Check out Robert's (username MP&C) posts for some really good info on patching panels.
Good luck.
