Latest update: When we made the connection to the upfitter switch, we accidently snipped the provided connector in half. So we had to cut off the connector from the wire and spliced them together, bare wire to bare wire. After twisting them together, I wanted to apply some solder to get a really good connection/contact on the wires and to keep it secure. I searched for my solder and could only find some plumber's silver solder (Oatey brand) that I had. I thought silver solder sounded pretty good and should work just fine. So I used that for the connection before putting the heat shrink insulation over the connection. Well I finally did a web search to see if there would be any issues using plumber's solder versus electrical solder. And the results were not what I was hoping for.
Apparently plumber's solder has some acid in it to help clean the surface really well to ensure a good bond. The acid can degrade or corrode the wires and cause a bad connection. So over time, I could lose the upfitter control over the S2 lights.
I do plan to add another light to the bedside soon. So when I make that connection to the upfitter switches, maybe I'll cut the old S2 connection out and redo it with the proper solder.
Who knew plumber's and electricians can't get along and use common solder!!