mount it on the back of a sceadu, and yes you will have enough cable to safely get to the rx.... ive been told that its the bast place for it, and ive got it there

the problem you have new is the 12 inches of wire (gyro to servo) that you have to hide....

as for using extensions, it will be ok, but remember if you extend from gyro to rx, then you need 2 extensions. one for the main control wire and one for the singe cable remote gain cable