Faster shutter speed can help, as well as turning on any sort of movement compensation the camera has. People do have twitchy hands after all. But yeah, you want to isolate the camera as much as possible from the heli, direct to frame is not good. Really you want it to be able to move in every direction independent of the heli, with dampening material at the joints. Just because the heli shakes doesn't mean the camera should. Then you could try lowering the amount the heli itself vibrates. Balance the blades and head really well. Make sure they track true. Use longer blades if you can, to compensate for lowering the head speed. Both should help turn high frequency vibrations to low frequency ones, while maintaining lift.