Aha! Thank you for the bunching/milking technique to clean up the gaps in the braid after splicing. This is something I've run into in the past and ended up with some nasty-looking splices, but never put any thought into how to solve it since I'm just making slings for myself and I don't care how they look as long as they work.
I've never bothered much with locking stitches for preventing slippage, I've always just used a brummel. What is your preference on that? There are situations where a brummel is difficult(for example if one end of the cord isn't small enough to pass through the braid without significantly deforming it), so I imagine the locking stitch would be easier there. There is also the twist/untwist method Acroballistics shows here, but again depending on the situation a lock stitch might be simpler:
https://youtu.be/9M2DGF2NUd4?t=486That vectran does look quite stiff for being a single cord. I've never used it before - does it soften up over time like dyneema?
Also, since we're on the subject here, there is another way you can do the double finger loop with just a single cord if you want to save on weight rather than doubling up like in your video. Run the cord perpendicular through itself just like in your video, but then curl around the other end and bury it into the other side of the other finger loop(see photos). I didn't do a brummel there, but you'd probably want to do that or a lock stitch so it doesn't slip out, although it's less likely to slip out than a single finger loop.
...although as I'm typing this I'm realizing your way is probably better anyway since the single brummel locks both loops in place and then you can just trim one end after the brummel and bury it as you normally would - then you wouldn't have to completely double-up your cord like I was thinking. Move along, nothing to see here after all