RE: Need help to modify a radio
KISS princible.
Get a cheap PC joystick. Gut it and keep the handle. Seperate the joystick. Take the throttle slider from the TX, extend the wires and using a dremel and Goop install it on the thump side of the joystick. Bevel the bottom of the joystick and glue one side to the RC TX stick. Screw on the other side. You may have to strengthen the gimbal springs on the Tx. Use a TX tray with metal shoulder straps to hold the TX.
Fritz