Update... the equipment came in! Now I get to play. Spent some time figuring out where I wanted it mounted, how to mount it, created a bracket, and did some wiring. Both the secondary Kenwood radio and the APRS equipment are independently fused, and power sourced together off a relay I can control with my APRS labelled dash switch. It's power source is my 14 gauge "Acessories" wire which is relayed and fused again in the engine bay and comes on with ACC.
The Kenwood mounting bracket, riveted to my bracket, keeps the unit off the carpet and allows air circulation. It's also positioned far enough back under the seat that it has breathing room up top too, but close enough I can reach the buttons from the side of the seat while standing at the passenger door. The TT4 BlueTooth module Byonics shipped doesn't seem to have a project box around it, so a co worker is going to 3d print me a custom one this weekend
Pics...