Not being a candidate for a Lying Contest....20 feet as a standard minimum height for NOE ffight in a Huey.?
Memory serves it was Three Feet in the Huey long before the Term was NOE and was called "Low Level" or " Contour" flight.
I know for a fact we flew lower than 20 feet above the ground (includes trees, brush, rice paddy dikes and road right-of-ways.....going around or between tall trees sticking up over the rest.
I can benefits to either style aircraft....Sikorsky Comanche or the Bell Tiltrotor but each also have detrimental characteristics to be considered for the Task.
The Tiltrotor puts the important bits higher due to the diameter of the Prop-Rotors in airplane mode....and certainly does in either transition or helicopter mode.
Commanche does not.....as it the Rotor system that is the highest part of the aircraft and it would have the smallest radar cross section compared to the Tilt Rotor.