I also start with a "V" and activate EXP in the Pitch Curve menu, but I have only ever had to use three points in the curve.
That's the beauty of it. If the RPM is too high at hover, pull the center down a bit. If it's too low, raise the center a bit.
If it's too high at full collective, pull the two top points of the "U" down a bit or add more pitch. If it's too low, pull a little pitch out.
Usually takes about three flights to get reasonable constant RPM.
Most of this flight was fairly close in, so you can hear the helicopter pretty well, and can hear that the RPM is pretty constant throughout the whole flight:
Watch at YouTube
Team KBDD/Compass Team Manger/Experience RC/Team JR Americas/WR Field Rep