There are times where I can be my own worst enemy, in this case of adding a power port to my 289 roadster, I thought and over thought this. Hours spent taking pictures, measurements and more measurements.....At 2am last night, I had a "KISS" epiphany, and then spent an hour or so and installed the attached:
Single port, can insert a USB adapter to charge my phone, properly wired with fuses and weather tight quick disconnects. Held on below the dash with one easy to install/uninstall velcro strap. Even with a close up shot, you can barely see it, and unless you are looking for it, most will never notice.
Swing it out from behind the downtube, and easy access from either seat.
Wish I had thought about this from the beginning, would have been done on a cooler day, with less humidity.
Thanks to all who responded.
Bill S.