Dual CAN GPS Receiver on large Big Drones

I have two Here 3 GPS on my drone. it is a relatively big drone and the GPS Modules are apart about 50 cm from each other. and They are connected via UAVCAN.

Before this, I was using Ardupilot, and using that I could explicitly assign the position of each receiver. but in PX4 it only asks for one position offset from me. why is that? How can I input GPS 2 position from CG?