Posi-Taps will work. I had several pulling power from the tail lights on my 2007 Vee, for 4+ years and many thousands of miles.
The problem I did have was that Posi-Taps are relatively bulky, and there was no slack in the factory wiring. Could not get all 5 Posi-Taps in place. I spliced in more wire, extending the factory harness so that I had enough room for the Posi-Taps, plus enough slack to get them connected. I was hooking up a couple LED repeater bars for brake & tail lights. There's a thread about it here somewhere.
I didn't know about Eastern Beaver at the time I was doing the above, or I would have avoided all that. I would have bought EB's brake and taillight tap/harness extender product, plugged stuff in, and been done with it.
This is exactly what I did, when I wanted to power the brake light repeater in my top case, on the new-to-me 2019 Wee3.
2017+ DL650 tail light wiring isn't too different from that of the 2007 DL1000. Almost no slack to work with.
Sure, you can order the correct terminals from Cycle Terminal & make your own EB-style adapter. You'll still pay for shipping, and will need a proper crimp tool to do it right. There goes your savings vs. ordering the EB adapter. You might even wind up spending more.
I suppose what I'm saying is, you may technically save a few $ DIY-ing an alternative to the EB product, but you'll pay for it in inconvenience and your labor.
Up to you whether that's a worthwhile tradeoff. I know it wouldn't be for me.
www.cycleterminal.com
