The U12 is supposed to have a self-adjusting handbrake. You just pull it up and down, say, 10 times with the button in. However, you can adjust the distance needed to engage it:
[ From the Gregory's Pintara/Corsair Autofix manual ]
1. Raise the rear of the vehicle and support it on chassis stands.
NOTE: On models with rear disc brakes, ensure the rear caliper handbrake levers are resting against their stops. If the levers are not against the stops, back off the handbrake lever adjusting nut until they are and then dpress the brake pedal firmly several times before carrying out the handbrake adjustment.
2. Remove the centre console to gain access to the handbrake lever adjusting nut.
3. Tighten the adjusting nut until the handbrake level pull is 9 - 11 notches.
4. WIth the handbrake released, check that the rear wheels are not binding.
5. Check the handbrake operation with the vehicle parked on an incline.
6. Check the handbrake warning light comes on when engaged.