Panning group busses on S5

[Rpro]

Mixing 18 tracks of drums on the S5 along with other instruments. I assigned groups buss 1 and 2 to a few strips. I send the kicks, snare and tom tracks to group buss 1 and 2 and assign the group busses to the mix buss and remove the source tracks from the mix buss. The source tracks are panned appropriately but there is no way to pan the group buss. The reason for this is to insert external EQ and compression to drive the drums hard. The issue is that the group busses are dead center. The pan button won't activate. On my DM2000 I can pan the group busses hard left and right.

I need a way to pan group busses. Any thoughts are welcome.

Thanks