Lap welds are sorta like "utility" welds. Not really finish work. Can be done yet not the best or final way to go. Not only a butt weld, but a hammer weld is by far the best and most accurate approach. This is done by backing up the weld area with a dolly and spotting the panel in place one weld at a time. While each weld is "red" it`s tapped with a hammer against the dolly to ward off warping the panel when the weld itself shrinks...in essence you "stretch" the weld. This takes practice to get the eel of how hard to hit, and in many instances takes a helper to hold the dolly behind the panel. When you have the process down to a science, very little filler is needed and routine rust prevention is all that's required.
