I can't understand why you would want to disable the HH gyro, but if you did & still wanted to keep the C-12 ESC installed in your AXE.

Then unplug the tail-motor from the ESC (white & blue wires), & reconnect tail-motor to the 3in1. Unplug the C-12 ESC from the RX, move orange wire (from 3in1), up one spot (where C-12 ESC was). Wrap some electrical tape around white & blue leads from ESC, they'll still have power if C-12 is soldered to battery connector (Deans plug).
Turn on TX, plug in battery in AXE, wait for 3in1 to arm, fly it for awhile (fighting the tail) and realize the stock RATE GYRO SUCKS!
Reverse the order above, & stay with the GY240, you'll be happier in the end!

Rick