I had a steel strip rolled to the correct radius and drew two repair sections in the computer that I had laser cut.....all in 6-7mm steel.
If you look closely at the arch bars you will notice the curve is not only bent in one direction, but also curves in the other direction, so I made a bending tool from some scrap steel and a long steel bar. This tool made bending the patches to the correct shape quite easy....with one end clamped in the vice of course.
