fabbing my up-pipe was alot of test fitting. On my pipe I had many different angles on both planes. One of the direction/angle of the pipe and two when you have two pipes that are curved with flat ends, rotating each of the pipes for a butt weld will give you a different angle also. So I mocked up a pipe with cardboard the exact diameter of the pipe. Another thing that I did was when ever I got two pipes that needed to be butt welded, I took a sharpie and made a straight line down both pipes.
As far as the duct tape. That flange was a bit loose and I needed a little spacer to make it hold in place. Then I cut away a 1/4" strip and did a spot weld, then another 1/4" strip on the opposite side and spot weld. That was enough to hold it in place.
