I do use the SS 2009 chicken loop, not the other parts of the SS bar. By center line I understand you are talking about the depower rope. I tested many different types & diameters, I am now using 6mm dyneema. It might not work properly with the original setup though, because standard 12 braid dyneema doesn't seem to hold well in the clamcleat... (I modified mine for above the bar trim, with different cleat, different trim rope, etc ...). I suppose 16 braid would work but I never got the chance to try.
The original rope diameter is about 8mm, so beware your dynamic stopper will not work anymore with 6 mm.
As for the end of the rope, no need for complicated splice, just tie a double overhand stopper knot and you're done. cf. http://www.animatedknots.com
I use to do a lot of splice, I am just tying knots everywhere these days. Just be sure to use the right one for the right purpose.
As for the bearing I use 3EUR skateboard bearings that will automatically untwist my front line for about 30 session. Can do 10+ more sessions in semi automatic mode
Depower rope longevity, I am now waxing it say every 10 sessions, it seems like it will last forever and it does not rip the skin off my finger anymore.
And you dont need a bearing at the Y, you can use a fixed steel ring all the bearing does is untwist the center lines, just remember to rotate the same number of times in both directions and you don't need a swivel.
Ouch ... just remember to forget that comment ... your 2009 SS chicken loop does the job. Edit: it doesn't work well if you are using the safety line though.