Kamikuza said..SonnyRider said..
I use this for mine
http://www.liros.com/en/products/productfinder/details/detail/liros-d-pro.html
I used the 4mm first and found it pretty good. I recently changed to the 6mm. I splice both ends. But like Greenroom says, no room for adjustment when it stretch's.
Um, it's a single eye splice with the bury being the whole length. You're not using a single length, are you?
The line that comes with the Jaybar is buried the full length and tied off at the end.
I've done a brummel splice both ends, tapering off to the middle of the 300mm line, so each has a bury of 150mm. It kind'a helps to centralise the block I use as well. I also soak the line in melted wax to help resist wear.
I CBA to take pictures of mine

but I have fitted a 6mm stainless eye nut in the holes on the bar and looped the line through them. Because I don't have access to cutting down a shackle bolt & drilling a new hole to fit the bow shackle like Greenroom has. If I could I would go down this route. Now Jay has them listed on the website

But the cost of delivery is more than the item cost. So until someone stocks them in the UK, I'm not buying them.
The 6mm line I use has a breaking strength of 4300kgs. The 4mm line I used has a breaking strength of 1300kgs. The 4mm I used for several months and has no real signs of any wear. Running the block it is super smoooooth.
The 6mm was an experiment to see if I could use it or not. So far it's been on for 5 sessions.