GPS Yaw with dual QZSS CLAS receivers

I am using Japanese satellite QZSS CLAS for PPP-RTK (sub-cm class positioning), the advantage being that no RTCM is required.

I would like to use these two CLAS receivers to achieve GPS YAW with two NMEA GGAs, but the Single Unit Systems and Master-Slave Antenna Offsets settings do not work.

Is it possible to achieve this without changing the source code?