With the 120 grit and on, the 1/3rd stroke(that's total length of stroke/diameter of mirror) with 1/3rd overhang (1/6th to each side) needs to be held to more rididly for a max. stroke.

Thanks Robert. I'm not quite sure what the "...needs to held more rigidly for max stroke" means. Are you saying that I need to more precise in the stroke, staying very close to the 1/6 overhang? Can you clarify, please.

Also, I saw a posting that is very similar to my problem. Post: (!!Got a rough-grinding problem!! posted by John Suback on June 13, 1999).

Is my situation different? The recommended method was to move the mirror on top to decrease the curve and grind toward the outside.

I think that I should I do the same and put the tool on top to reduce the curve of the mirror given that I am already at the desired depth. (right?)

I calculate that I need a sagitta of 0.078206 and I can get a 5/64 (0.078125) drill bit under a straight edge so Im 99% of depth.

So graphically, I need to remove material where the dots are in the diagram while maintaining the center depth.

0.. ..0 00.. ..00 0000.. ..0000 00000000 00000000 0000000000000000000000000000 0000000000000000000000000000

I'm feeling confident about moving the tool to the top and reducing the curve. I think I'm on the right track here.

Thoughts?