I thought I'd sew up a few LED sequins as a test, just to make sure this works and to see how these connectors will fare.

5 LED sequins sewn to a piece of felt - nothing fancy.

The back of the stitching - just a simple parallel sequence.

So I got that part done, but when I started trying to attach it to the connector loops I had made, it became apparent that I would need to reconfigure the loops, and give them a bit more breathing room. With them both jutting out of the side, the threads were just too close and kept touching.

So I bent the connectors around a bit:

This worked much better. I think that on the next go-around, I'll try pulling out one of the middle pins so I can orient the connecting wire to the right side a little better. (The other 4 pins are just giving physical support - I'm not connecting them to anything.)

And we have light! Wheeee!