Have you made any progress with this at all? I too am intending installing a 7100 and want to run H.F. APRS but possibly through a dedicated 10MHz transmitter/ transciever. I'm interested to know what is a suitable TNC to use and any other kit that's required?I have gotten the APRS bug again thanks to this but let go of my aprs radio a while back, so have resorted to aprsdroid on the phone whilst around town.
I'm part way through a icom 7100 install in the rig and was considering trying in on HF. I'll need to buy a TNC to get it to work.