Course lengths as stated on the cluesheet were off by 50% (courses longer than advertised), as if the lengths had been calculated assuming the map was at 1:6667. I suspect that what actually happened was that the map scale is 1:15000, and the print scale is 1:10000, but that the map scale in the course setting file was set (by default) to 1:10000. That would also explain the big control circles and numbers. Confusing? Such is the price of versatile, powerful technology.