ADS-B in: Reducing data rate


I’m looking to add ADS-B in to a UAV. I’ve been looking at the ADSB_VEHICLE mavlink message and it sends a lot of information that won’t change or is unlikely to change EG ICAO address, callsign, squawk code for every single message. I’d like to change this so that this information is sent once, and then only the ICAO address is sent each time. I’ve created a new MAVlink function and .xml file for this, and now I’d like to find where the ADS-B in hardware is handled to add this feature. Does anyone know how I could go about finding this?