Thanks again guys, I think most students are going to be happy with the increase in rotor efficiency as a result of ground reduced inflow. That won't cause any urban myths to be propagated, and at the same time ensures they have a base of knowledge and tools to find out more if they want to.
Matt - you've left it dangling a bit, what a tease - are you implying that a quantitative analysis of the situation would lead to better insight ?