[Al Skierkiewicz]

fmercier,
We need to know how you are generating the full reverse throttle. If you are simply using a joystick then you have to calibrate to that joystick. If you are using a code generated full throttle reverse then I would double check your code.
What color is your controller blinking? There is a whole list of possibilities if you examine the manual. If it is blinking Red then that is an indication that you are not at full throttle but are commanding a reverse proportional output. That sounds like what you describe. The full on LED Green would indicate a full throttle forward output.