Tommorrow I am going to weld up a large " C " clamp. I have to go buy one that has a 6" or 8" opening.
I will cut the ends off and weld them onto two 24" X 1 1/4" x .090 wall sq. tubing and these 2 pieces will form the "open" end of the clamp.
At the closed end of the clamp I will weld in two 8" long pieces of the same tubing , side by side, & this will give me an 8" distance between the long arms.
Next I am going to sand and plane a pair of 8" square wood forms that will lay on the top & bottom of the segment. These wood peices will conform to the roof contures. Then I will glue a piece of 1/4" steel plate to the flat side of each wood form. I may have to make numerous wood forms but I will see.
This will allow me to use the "C" clamp as a compresion press.
I believe this will give me a very smooth surface.
As I have the roof vent out, I can use the clamp by utilizing the vent opening.
After I get the clamp built and a trial run completed , I will post some more photos.
This is all a theory, so we shall see what we shall see.