Truing the back surface.
I'd see what can be done with ring tools. 1/4 diameter for initial local grinding and 1/2 diameter to finish. Car wheel rim for the 16''? I used a 1/2 D aluminium ring to alter curvature on an 8'' and the spherical surface seemed true. Shouldn't take long.
Edited by davidc135, 26 October 2021 - 02:31 AM.