That link of yours to those bluestick images made me feel cold just looking at them !

I have used very small micro servos on gyros up to about 36" rotor diameter. The forward and aft tilting servo (pitch) tends to take the greatest hammering and generally speaking takes the larger loads. Any rotor system larger than 32" diameter I usually use more standard servos like Futaba 148 or 3001.

One tip, if you can mount the rotor mast fractionally behind the axis point where the head tilts fore and aft this will offset a lot of the strain on the pitch servo. Its called an offset gimbal and is used on full size gyros to ease the workload on those poor sensitive pilots

Aileron axis is usually not quite as stable as say a fixed wing trainer model. You can improve things a bit by having a lower centre of gravity by say having a higher rotor mast ?! Mind you if you can put up with it I find that its all part of the challenge.

If you want design and flying info take a look at www.autogyro.com Most of what you want to know is in there if you look hard enough. www.gyronuts.com is another useful place for general info.

Sean