with a joystick impossible to have horizontal=1 and vertical=1 at the same time

I have an XBOX 360 controller and when I put the joystick in the upper right corner I expect to have horizontal=1 and vertical=1 but it is not the case.

I’m working on a 2D scrolling game and more the stick is up and less the ship speed is important (altitude of the ship is based on vertical (1=top of screen) and speed is based on horizontal (1=full speed) => I’m not able to go on the top of the screen at full speed…)
Do you know if it is possible to configure the input to have this situation or do I have to manage this by script ?

If it must be by script : is there already some examples to help me ?

thanks in advance for your answers

Well I applied a multiplier to horizontal and vertical (here 2.5F) and then limit them to [-1…1] and all is working well : when I put the joystick in the upper right corner I have horizontal=1 and vertical=1