The REVO on my heli does help quite a bit. I set up the proportional on the 4-in-1 to hold the tail in a hover and then set the revo on my TX to a switch so I could see the difference. I'm still playing with values. I am currently using a high of about -20 and a low of -15. The difference is quite dramatic between having it on and having it off. The heli lifts off without any need to touch the rudder with it on. With it off I'm flying the rudder during takeoff. When I flick the switch on there is a noticable change in the rudder trim and I have to retrim it. Not a big deal but just something to be aware of. The higher the revo settings the more you have to retrim.
Here is my take on REVO. I could be completely wrong in my understanding but so far this has been my experience.
The gyro is working after the fact trying to correct what it has detected. There is a lag time there. The TX is working with known inputs and can more effectively counter but you have to take the time to tweak it to get it right. So basically the stock 4-in-1 gyro and the TX REVO settings work together to make your heli more stable. The 4-in-1 gyro will now become the stabalizer for wind changes and stuff and the TX will handle the throttle changes.
Here are all of my settings currently for my Futaba 7CHP. I am constantly tweaking:
D/R, EXP
1-AIL down - D/R: 140, EXP: -5
1-AIL up - D/R: 140, EXP: -0
2-ELE down - D/R: 140, EXP: -5
2-ELE up - D/R: 140, EXP: -0
4-RUD down - D/R: 100, EXP: -5
4-RUD up - D/R: 100, EXP: -0
All ATV's/End Points 100% (until final setup item posted below)
SWASH:
Aileron -80%
Elevator +80%
Pitch +25
REVO (set up on a switch to turn on and off for testing. I'll probably try out the higher values as well)
HI: -20
LO: -15
Normal Pitch curve: 40,40,50,75,100
Normal Throttle curve: 0,25,50,75,100
Idle Up (1) Pitch curve: 0,25,50,75,100
Idle Up (1) Throttle curve: 100,75,50,75,100
Idle Up (2) Pitch curve: 0,25,50,75,100
Idle Up (2) Throttle curve: 100,100,100,100,100
I've not had the chance to really test the idle up settings yet but testing on the bench works exactly like I want it to. It will be interesting to see how it does in the air. The only final thing I would do is set up the throttle hold so it stops the motor
The big trick to getting this to work is this quote from Gary Hoorn:
The final setup touch that makes this all really work nice is to remove the main blades and unplug the tail motor. Now in Normal Mode spool up the Heli with the Tx in Edit Mode for Channel 3. Go to full throttle and the Red LED will be on solid. Now dial down the high end point on the throttle until the Red Led goes out and it turns Green. Go back up on the Throttle End Point about 5% from this point. Now the Red Led should come on just as you reach full collective/throttle. In the Idle Ups it will come at each end of the collective.
When I did the above my final positive endpoint for the throttle channel was around +37%. It had to go down quite a bit from 100%.