I would'nt recomend such solution.
For normal, hydraulic pressure measuring devices like RAVAS or NEXO
the weighing process of the load goes like this:

You get the load, raise it to some prescribed level and push the button. The load goes down (40-70 centimeters - depending on the calibration) and the weighing process is done - you get the result on the display.

Just imagine, that the you exceed the maximum load 5 kG and system will totally shut off your truck with the load raised, somewhere in the middle of the aisle. Total disaster.

I'ld rather trust your truck. When you exceed the load ~ 20% while lifting, the relief valve should simply open and disable the lift.
Or, as PPPA suggested, calibrate your weighing device maximum load on higher level and install some beeper.