I generally butt weld patch panels And slick both sides. And only do rosette weld at pinch weld spots. The aftermarket panels are usually thicker than the origional for one reason or other. Start the weld on the thicker, and work toward the thinner. With a good mig, set properly, it happens very quickly, no time to lollygag around. just pop pop pop and it's tacked in three spots. then continue making pops about 2 inches or more apart, then come back and pop some more, untill you have a continuous weld. Grind flush, and prime.