Don't try to run a continuous bead. Skip-weld in several areas, never more than 1/4" at a time, and move several inches away for the next stitch. That keeps from distorting the panel due to big temperature changes. It also helps if you have several patch panels test-fitted and tacked into place so you can switch to another place and make a few welds while things cool down at the first weld site. Then go back with an angle grinder and smooth up the weld beads after some cooling happens. Definitely run the smallest wire you can find, hot and high speed.
Jerry
