kunix: Like you expected, the rgn in boot.bin reported that it was successful.

Now's here is where it gets interesting...

The rgn in fw_all.bin folder actually started updating the device
(it finally looked like it was actually doing something as percentages actually were incrementing in smaller increments).
It completed and it said it was successful.

Currently the Nuvi 1390 screen shows: Loader Loading...

I have not powered off and powered device back on yet.

Very promising, next steps?