I have never had much luck with crimping curved metal. I prefer butt welding curves. I weld a small spot, then bump the metal to where they meet and then weld another small spot. The clamps don't work as good as it appears in catalogs. I have sheet metal screwed sheet metal to something like 1/8" strap bent to the correct curvature with pretty good results. But the whole trick is to weld small enough spots to prevent warpage. I would try to repair what you have before you do anything. You might read this book.
http://www.amazon.com/Key-To-Metal-Bumping-Book/dp/B002S4Y7RS It is almost 60 years old, but it is still very much on point. Something that is not mentioned in the book is a shrinking disc. I have had good results using one. Repairing previous repairs usually involves shrinking stretched metal.
