Project completed. It works.
Minimalist implementation of RFM69CW shield for a Wemos D1 Mini. Final build uses just the PCB, the RFM69CW module, two 5-pin headers, and a length of wire to serve as the antenna. This minimalist design both simplifies assembly and keeps the PCB cost low.
I do not plan any further changes to this design. This project is marked "Work in Progress" only because I sent the design files off to the fab just this morning, and, therefore, I have not yet received the fabricated PCB back for the build and final test verification.