It's not the best solution but it's better than nothing and paint will just burn off and make your welds that much uglier. And use a weld thru primer before you start welding. Then I say plug weld and lap weld and seal both sides. The factory often spot welds places like this, but most places won't have the equipment to duplicate that. That's not to say there isn't a time and a place for a lap joint either, where panels have to overlap like a seat re-enforcement or where a floor pan meets a rocker. Are we looking at a body line? It almost looks like you could cut away the existing metal and tuck that flange behind if you prefer a lap joint, but if that's a body line then I would say that's a bad idea because once you weld, your body line will almost disappear. I don't know how that panel is supposed to look when finished. You're not really saving yourself any time either because now you're welding both sides of the panel so even though you have a thicker joint, you're putting that much more heat into it. And unless you're gonna take the lazy route and just use some seam sealer, then it's going to take twice as long to weld. I don't care for a lap joint because it leaves a space where rust can form on the inside if it isn't sealed properly. Depends on what you're trying to attain, really.
