I really have no idea at all, not even a wild guess. Too high of an RMP versus vertical velocity will result in airfoil stalls and a turbulent "shadow" for the next airfoil in line. It could at some point in the ascent even become more like a super-draggy spool. If so, I'll reduce the airfoil count to three and also reduce their angle of attack while keeping the motor tilt at 45 degrees.