As a IP check pilot I personally would never rotate a IV at 65K.   I find
80-90K to be more realistic given the loading condition of the airplane.  My
preferred method is to raise the nose wheel slightly off the ground, hold
the airplane steady and let it fly off the ground.  The airplane is stable
in this condition and accelerates easily.    The original factory IV, 409L,
was considerably lighter than the planes that we are building.

Joe