toecutter

I recently put a new skin on my driver side door. It can be slim pickings finding good rust free two seater doors in Australia. The skin fits well in all areas except the front bit that sits directly behind the front guard. The gap there is about 3-4mm too big. The skins are aftermarket and no further alignment is possilble as it sits perfectly apart from this. If i once again remove the door from the hinges, is it possible to weld a thin strip of metal to this section to add the additional 3mm and get the gap correct??? Would this be difficult? I thought i might be able to weld some wire along the edge and get a nice flush finish with body filler. Looking at the passenger door I can see that this new skin is just a little shorter in that front section to leave that ugly gap.