THIS IS A WORK IN PROGRESS
Current Settings: 2kbps
Proposed Settings: 2kbps
{ RFM69_REG_03_BITRATE_MSB, 0x3E}, // 2 kbps { RFM69_REG_04_BITRATE_LSB, 0x80},
Current Settings: 12kHz
Proposed Settings: 5kHz
{ RFM69_REG_05_FDEV_MSB, 0x00}, // 5 khz (10 khz shift) { RFM69_REG_06_FDEV_LSB, 0x52},
Current Settings: 128kHz
Proposed Settings: 10kHz
RFM69_REG_19_RX_BW, RF_RXBW_DCCFREQ_010 | RF_RXBW_MANT_24 | RF_RXBW_EXP_5},
See section 3.4.6 in the RFM69HW-V1.3 datasheet