Overshoot with perfect circle O is trickier than overshoot with a more flat bottom O. You are trying to ballance the perceived mass and distance of that mass from neighboring glyphs. It may be more an issue of font metricks. Try your problematic sizes with tighter and looser sidebearings and see what happens.

ChrisL

There is indeed a purely circular arc on the O (and such). At this point the sidebearings are equal to the counter width. I hadn't considered mass vs. distance. I know we are referring to a perceived "mass", but I wonder if it isn't just like physical engineering where linear dimensions and mass don't scale together. If so, there may be no solution for under and over 1" usage? I will experiment with it a bit to see how metrics alter things.

Think of mass having gravitation in the opposite direction. The large mass of straight sided glyphs like H repells and needs more sidebearing. The small mass of circular O sides needs less sidebearing. It is kinda' like balancing a heavy weight on a teeter board with a light weight by extending the fulcrun of the small wiegt to ballance.

ChrisL

Would you say to adjust the sidebearings prior to the overshooting?

Choz, it is a ying and yang thing to me. I just go back and forth with a few key glyphs in a test word until the thing binds itself together. There is nothing absolute enough about type design for me to be able to set up a step-by-step procedure. Everything stays plastic and nothing is imune from change until it lets you know by seeing. Of course, that may be why I never get anything finished :-)

ChrisL