I'm not a heli guy but as I understand it cyclic servos are not limited to any size, they are just servos that are lightning fast AND powerful to control helis with more speed and precision. The term cyclic just means that they move the swash plate back and forth very quickly in response to gyro and pilot input. They need to be fast and strong to change the pitch of the blades under load.

I use a JR 8717 for my Baja's throttle/brake and it's awesome, snappy throttle and powerful brakes with a single servo. I think that servo may be too fast for steering, but I guess it depends on what you're using it in.