We've just got a new team room at work, which has a few board games available already. I'm planning to add 9x9, 13x13 and 19x19 go to the existing collection.

However, the mix of skill levels is pretty wide: some, like myself, have a fairly good idea of their ranking in the wider world; the vast majority will be beginners; and there's a fair sprinkling of people who've played a bit and probably fall into the 18-25kyu range.

I'd like suggestions for a simple scheme that I can use which should ideally have the following properties:

• Gives ranks which are generally good-enough to work out a handicap.
• Allows me and others with a well-known external rank to act as fixed points (or at least fixed-ish). This is so that the others can tell roughly where they are if they feel like going to a real go club.
• Copes well when the majority of the games are 9x9 and 13x13 rather then 19x19. Tea breaks tend to be short.
• Isn't too complicated to explain and maintain.

Any recommendations?