-- non-subscriber, please reply to sender and MMD --

I have had some success removing dimples from discs by placing
the projection side on a piece of 1/8-inch thick foam rubber sheet.
Next, take a cylindrical-shaped tool, such as a glass jar or tin can,
and roll it back and forth over the distorted section of the disc.
This is similar to rolling out dough with a rolling pin or using an
"English Wheel" in metal forming.

The foam rubber protects the projections, yet offers enough support
to allow straightening of the metal.  A bit of experimentation may be
needed to achieve the desired flattening.  Good luck!

Knowles Little