Ah, I had thought it might be something like this. You raise a good point - the grace distance could well be 15.81 - I've never actually got round to modding the campaign map to find exactly where it is. Perhaps when I have more time.

PS I've sent you a couple of PMs over the last few days about your suggestion for the Ludus Magna forum. The board had a bit of difficulty during that time, and I'm wondering if you got them?