question about back of a mirror in progress

Hi,

The "mirror in a day" post, which was wonderful and enjoyable,
inspired me to speak up and ask a question about my own project.

I'm grinding an 8-incher and it happens to be my very first effort.
It's a little stressful not knowing if the surface is really good till
I get it far enough for reflections! I'm doing it at a nice leisurely
pace, too (read "spare time").

Anyway -

When I was just starting it and as nervous and clumsy as any newbie, I
accidently did some work on the wrong side with #80 carbo. Not very
much, but now there's this kind of ugly area in the middle of the back
that spoils the appearance, at the very least.

How important is it to get rid of this by grinding the backside to
evenness on flat glass or something? Will the messy appearance of the
back, affect testing done pre-aluminizing?

Thanks people!

James