Every F-18, F-15, SU27 and Mig 29 that I have ever flown has that massive rudder to roll coupling mentioned above. I personally think its too big a task for a gyro to eliminate that ( Certainly without messing with the flying of the model )
I look at and use Gyros in "certain" models as a damper more than anything. The cougar is a classic example. I have owned three of them now, and only one was not equipped with an aileron gyro, and it was visually obvious, as it used to fidget almost all the time. An aileron gyro sorted that, and if personally I will never set a Cougar up without one.
The way I look at it is that we spend all this time, money and effort to make our models look as scale as possible on the ground. Every rivet, panel line is applied as standard now almost. We fit out cockpits out with all the dials, and gauges.. we even make inside of the gear doors scale now a days. I see it as a shame to see all of that accuracy in scale fiedelity wasted as soon as the model breaks ground.. Where it proceeds to wobble, fidget, shimmy and shake across the sky [:'(]
I often show people a demo when I have a model with a gyro fitted. I will make a few laps with the gyro on. Then I turn it off ( I always have my gyros switchable from the tx) I then make a few more laps.... The difference is always very obvious! In the same demo I also bank the model hard over to one side and let go of the sticks.... Just to show the model diving toward the floor of its own accord.. That is to try and put across, how my gyro set ups work as just a dampener, and without the input from me that particular model will ( If uncontrolled by the pilot ) hit the floor just as quickly as the same model without a gyro. It does make me chuckle to hear comments like " It only flies like that as it has a gyro fitted" I never use heading hold modes in any of my gyros, as I hate the feel that a gyro is infringing on my flight controls.
I also find gyros to be very model/ type required. Right now in my display models, I only have two equipped with any sort of gyro. I find the others just dont need it as much. Some models just have better natural stability than others, so I dont bother fitting them. For example.. My T-33.. That has the feel of having a gyro fitted to the ailerons, when infact it is just super locked in on the roll command. Flip side of that is my Airworld Mig.... Those thin, short wings never ever seem to settle without a gyro. Yet with a Futaba 351 fitted they just dial in perfectly. My Skymaster Vipers ( Both big and small ) are super solid on all controls, where as my Epic Victory was a wobbly thing ( Especially in a wind) till I fitted a Gyro to the ailerons and rudder.
I have had a play with quite a few different types of gyros. I know my sponsor may not like to hear this, but the best results for me have come from the Futaba range of Aero gyros. Those with the GY prefix. GY 350, 351 and 352. I tend to favour the 351 as most of the time I have only used a gyro on single axis. Although I have set a few customers planes up with the 352 which is dual axis ( So I can cover Aileron and rudder through the same unit) The 350 is basically a re branded 401 heli gyro and works really well on a single servo application such as nose wheel or rudder.
I like the 351 as its an ideal aileron gyro. It has dual in puts and out puts.. So you can still have individual aileron servos. Its gain adjustable via the TX.. It does require an extra channel, but in my opinion its well worth it. I can adjust the gyro gain in flight ( if you fit it to a slider or rotary dial) although I tend to have mine set on a 3 position switch Two positions being off, and then last position being on.. I do this to make sure there is no way I can have the model set in AVCS ( Futaba for heading hold) I then just raise or lower the ATV's till I get the gyro set up which I am looking for. Thats one where the flight control does not wobble, or bounce or hunt which it can do if the gain is set too high. I have used the Futaba gyros without using the gain control, as the gyro unit itself has manual rotary dials that you can set it up from, but I like the tx switchable option... if only for the ability to be able to turn it off in flight and adjust it easily.
The main reason why I use the Futaba gyros is that I have found them to be the most accurate, and least effected by "drift" Drift will show itself in the form of the model needing to have trim adjustments made to the control which the gyro is fitted. Some one more intelligent than me will explain how and why this occurs. All I can tell you is that the Futaba Gyros I have used have suffered almost 0 drift, and when it did occur it was a tiny amount resulting from me flying in some environments with big temperature changes.
Sorry to make the post so long winded, and I hope it is of some help?
Regards Al