I've been working on this car for quite a while, the roof had a huge dent, It's pretty obvious that the car got crashed years ago and was poorly repaired by a body shop who preferred to use a ton of filler instead of fixing the damage .
So I took the area to bare metal, the dent was so deep and since you can't really get to the back of it because of the metal structure of the roof, I decided to replace the part and weld on a new piece of roof, it's better now, but I think the metal on the roof was stretched due to the crash and/or bad repair job and it's a bit warped . I can push down on it to align it and weld it to the new piece, But I think it would be preferable for it to be aligned before the welding . but there is still the same problem, I can't really get to the back of that part . the new part is perfectly aligned on its 3 other sides though .
The first picture is the gap between the new piece and the rest of the roof, the second one is when I push it down, What do you think would be the best solution to this problem ? thanks a lot for your help !