I`ve seen many factory style installation with cracks so I decided to weld it up and grind back it to original looks. I don`t like the seam gone, but I don`t like cracks either. Can`t tell if it will hold since I`m still building my car, but I`m pretty sure it will.
take your time welding and it won`t warp. If you make sure you have the panel welded in the original spots as well, I`m sure you can fill the rest with bondo and won`t get in trouble.