Your motor tuning determines your rapid speed and you dont want to adjust that as it could upset your motors making them stall etc.
If you are just wanting to use the full Jog without having to press the Shift key then yoiu can. Press the Tab key and you will get a flyout, set the slow Jog to 100% by typing in the DRO and pressing the enter on your keyboard, now when you jog without presswing the shift key it will be at full rapid.
Hood