Rfd900 Txmod and Tandem x20 Lua

Hello All,

Ive been an avid reader but first time poster. Ive been doing some system upgrades coming from some original frsky taranis radios. I purchased the tandem x20. So far loving the radio. I have also switched over to the rfd900 txmod v2 following years of good results from rfd as a standalone telemetry radio.

My planned setup was going to be an ardu Antenna tracker with the txmod mounted and then hardwired to my x20 running yaapu scripts. I am however having a difficult time using either the module bay or the eternal top s.port. I have had sucess using an r-xsr as a repeater like Yaks setup. Id prefer to run hardwired for simplicty.

The things I dont understand are the compatibitlty of S.port and External PPM. Also, when selecting external sport in the yaapu telemetry is that meant to be the top port or the module bay?