OK, I have modified the library so that GPIO0 and GPIO1 are set to follow tx_state and rx_state respectively, and updated the doc to show connections from GPIO0 to TX_ANT and GPIO1 to RX_ANT.
After doing this I saw abut 5 db higher output on transmit at higher levels with my RFM22B-S2
New version 1.7 of RF22 library is now uploaded.
Feedback please.