Hey Jeff,
Try this, if you haven't yet.
When you set your GB, use frequency 2 and get it as neutral as you can, then use freq1 to hunt in disc.
I'd like to find out if this can be used as a standard method for optimizing GB for best depth and discrimination for the C & V. A coin garden can help to confirm test results.
If you haven't heard, I think it was Monte who suggested setting your GB slightly negative to hunt in disc. (for the C & V) I did some extensive testing in my coin garden and found a predictable change in the polarity of the GB when the frequencies are changed. I thought that this might help out those who swing an unmodded C and change coils often.
Some Tesoro users like to get the maximum performance out of their unit and others are content to have a silent discriminator. After reading your post, I figured you would like to get the most out of your treasure finding tool.

Modded Cibola W/10turnGB+ AM Trigger Switch+ Volume Cont.+ 9X8+ 5.75C