Thanks for the reply Jeff,
I used wireshark for the measurement.
To switch to native with no transcoding:
Would it be as simple as replacing the gc_Listen(linedev_a, timeslot_b) and gc_Listen(linedev_b, timeslot_a) with dev_PortConnect(ipmdev_a, ,,,) and dev_PortConnect(ipmdev_b,...) as well as replacing the corresponding gc_UnListen()'s with dev_PortDisconnect()'s (with event handling as needed for the dev_ functions)?