"The "Needle Valve Adjust Mix" is the best and most user friendly manner to synchronize two engines on a 9C."

Recently set up the 9C for my twin - came up with the same conclusion - then spotted this thread.
Works great, and lots of control for endpoints, in flight adjustments with Vr knob, syncing throughout throttle range with the needle valve adj. Need the 8 channel receiver.

NE AERO Twin Air