Understand failsafe and how it effects your gyro:

On a DX7 the most important failsafe is at signal loss and this is throttle low so that if you lose signal your throttle turns off. When you bind it remembers the position of the throttle for signal loss and the remaining servos position to use before you establish a connection between your transmitter and receiver. The reason it is important to ensure your trims are centered at binding is because the gyro initializes before the signal is established. So if you are trimmed on your rudder channel your gyro will always be off center. Make sure you understand how this works. In fewer words when binding center all your trims and put your throttle to low. Make sure you gyro and tail servo are plugged in. Then bind and you are all set.

On Futaba you set failsafe through the menu so check your manual.

Ensure you are at center stick and getting servos at 90˚: (Get your servos moving the correct direction first)

I like to set a pitch curve that that will protect me from bumping the stick but you may also just go to the pitch screen of your radio and set it for 50 in/out or however it is on your radio. Before we set out servo arms to 90° we want to ensure we are at center stick. Setup a pitch curve to be 0, 50, 50, 50, 100 or 50, 50, 100. If you are using a 3 point radio you will have to check max throw with another flight mode. Now get your servos as close to center by swapping servo horns around without using subtrim as possible.

Setting your swash height to 10mm from the top main shaft bearing block:

Next another point that is  do not setup your swash using the hair below the stops method such as commonly suggested. This is imprecise and time consuming. Cut a little rod that is exactly 10mm long to use so that you can get your swash centered. Get it as close to 10mm as you can between the top main shaft bearing block on your frame and the bottom rim of the servo at center stick. You do this by adjusting the 3 servo rods between your servos and your swash. Yes you will end up with about 1˚ difference in pitch on the Trex. This is normal for example +10/-11.

Gyro servo travel adjustment 102 by HeliSmith

It is commonly suggested that you either adjust your servo in rate mode until you can hover without a drift or you set your tail blades flat and let HH mode work it out. I do not find good results under extreme conditions using these methods. Here's what I do.

Get into rate mode 0 gain rate mode however you can on your radio. You may have to turn down your gyro travel limit first. When giving full rudder in both directions adjust your servo on the boom until you have just a hair gap equal in both directions between the tail pitch slider and the hub / tail case in both directions. Adjust your gyro travel limit and move your servo until they are both a hair away in both directions. Lock that servo down and don't forget training gear is your friend when testing your tail. Never fly in rate mode if you used my setup this setup is now strictly HH mode period.