sounds like your esc is calibrating midstick as 100% input, so the esc is "failsafing" beyond its percieved 100% limit as you move the stick right past midpoint. ideally the rx/tx should be bound before the gyro enters it's calibration routine, and the gyro should be ready before the tail esc starts it's calibration routine. the reason for this is if either the gyro or the dx6 "blip" when the esc is calibrating, the esc may read something other than the gyro's max/min output as it's end points.

the esc needs to see the true max & min of the gyro during it's startup routine (using full left/full right/full left inputs). you could try installing a power switch (or a plug) to the tail esc. it would allow you to power on & initialize the tail esc after the gyro is ready to go.

btw, i'm sure you already knew this, but you're tail will likely spin even with the main motor off once you get it setup correctly. this can make unplugging the battery unsafe, but you can use a throttle kill switch programmed to give full left rudder while you unplug. just make sure it's not active when you startup the heli.

-kev