Help with OEM fork of RFM69_LPL + AVR128DB28 (and maybe someday ATTiny84)

I finished creating a TinyTx firmware sketch for RFM69_LPL. I posted it in a topic, because I have some questions specific to that project.

RFM69_LPL firmware for Nathan Chantrell’s TinyTx with ATtiny84 - Emoncms - OpenEnergyMonitor Community