Stan; thanks for these two very good ideas. You are the master of timely helpful suggestions!
I actually have in my user notes that the grounds must be kept isolated, and that if the supply is DC you can just jumper the bridge rectifier pads. But I never considered the idea of adding a simple diode to the + side and jumpering the ground side to achieve common-grounded half wave rectification. Think I'll go back and add that to the user notes.
The insulated 317P is also a nice option. I checked Digikey and they can be had for less than $1, compared to anywhere from $3 to $5 each, and more, on ebay. So definitely DK is the way to go. I'll also add that to the user notes.
Thanks again for your valuable input!