Hi there, I don't recommend to tamper with the board. It might get damage during or after the modifications. The information from the User Manual states that the device can sense DC signals of at least 11 V. Instead of modifying the card you can add external circuitry that sends valid high logic levels to the card every time receives 5 volts (ex. transistor, relay, etc), that way you can be sure that the integrity of the card won't be compromised.
Alejandro C. | National Instruments