[hewittca]

I think completely eliminating that seam is a bit more of a challenge then what you described, as you pointed out. Even for the guys who weld it up, I've seen where they actually had to re-radius that area to get a smooth transition. I think the problem stems from the fact that the area really isn't a smooth transition to begin with, as there is a slight crease in the roof along this line if you were to just weld it up and grind it smooth. For instance, here is an example of an actual seam filler panel that Scotts Hotrods was offering at one point. You can see that they actually cut that whole region of the roof out and fit this smooth radiused piece in its place.