I place the following disclaimer on all of my maps:
"RaceMeasure has measured this course following USATF guidelines, and stands by the measurement.
However, RaceMeasure does not set out the course on race-day, and is not responsible for courses not set out precisely according to this map."
I have had no one emailing telling me I mis-measured a course since I started putting that on all maps. I did receive emails telling me a race did not run their race according to the map, however. It was just an informational email, and not someone seeking my hide.