Here are the results of our flybarless TRex 450, 6 months after putting it away. T-Rex 450's can fly without flybars or weighted blades. The servos have to run at over 50Hz, maybe 60Hz, or better yet, digitally.
The servo frequency was the most important factor. Unfortunately, the direct swashplate coupling may have put too much load on those HS-65 submicro servos because they burned out constantly. The right front cyclic servo in particular was very unreliable. The sign of a dying servo was random nose dives.
It got 10% more flight time without the flybar & crashes were much cheaper.
Unfortunately the cost of those submicro servos & the mechanical parts doomed it in favor of a tri rotor, total electronic stabilization.