The first tool is the rivet gun and narrow tool. the smaller tip area gives higher psi. I start at the intersection of the tubes and work up the edge of each tube, but not along the long straight bottom. I then go across the bottom of the tubes and work toward the top to get the forming started.
There is a wrinkle starting at the top because I went to far with the bottom dowel.
We'll see how I do on the next one. At this point it's time to go back to the inlet tubes.
It turned out the anvil on the 6" c-clamp was to big and the clamp kept sliding off the edge of the plywood. The adjustable clamp worked better. Even though you can't get it as tight.
You can see from the top view how well it worked to let the steel slide into the bend along the straight bottom edge. The cuts into the corners where the tubes join worked very well to let the steel slide into the tubes.
They all fit perfectly. I didn't have to re-drill a single hole.
Time to make another shell.