michaelr - I read him to mean that if you type "A" and show it in his font, you'll see the "fingering for A" instead of the "character A."

I don't know whether it will be useful, but Microsoft's Typography group offers some general assistance for development of True Type and/or Open Type fonts. If you have a decent "font builder" program, you really shouldn't have to worry too much about the details of the font specs, but there is some "general info," some "helpful hints," and according to the index, some recommendations on available software. They should have some info on what "features" need to be defined to get the character sizing you want.

John