Dynamic rope for Kong Slyde DIY tether?

Am looking for recommendations for specific dynamic rope, purchasable by-the-foot, for a Kong Slyde DIY tether per the Alpine Saavy article below:

https://www.alpinesavvy.com/blog/diy-tether-with-the-kong-slyde

I've searched,  found a Reddit thread and post that says 9mm "barely moves". The article says "8.5 mm or 9 mm dynamic rope is the best choice for this". Would like to hear from anyone who is using the Slyde this way, what specific rope and diameter works well, what doesn't, and where you've bought the cord? 

Thanks in advance!

Btw. I HAVE read this thread https://www.mountainproject.com/forum/topic/112316418/kong-slyde-as-an-alternative-to-the-petzl-connect-adjust, which doesn't address my question.

Go to a gear shop and try their cords in the slide. I used an old 8.2mm half rope piece for a while before switching to the Adjust buckle with 8mm cord. Throw an overhand on a bight at the end of the tether and you have the fastest possible way to clip into 2 bolt anchors.

9.9mm is wrong. I had to chop part of my rope so I tried it out. Definitely try out the smaller options

Email John from Alpine Savvy. He’s pretty responsive and also is active on this site. 

Just set mine up yesterday with a length of this rope, which seems to slide well enough. It definitely moves when cinching up, and doesn't take too much fiddling to release and lengthen the tether. I've only tested at home, but at some point I'll be able to get out and test it in a real climbing scenario.

^ Thanks, Peter!

Other than the rope you mentioned, I am very surprised how difficult it is to find 8.5–9 MM dynamic rope sold by the foot!

https://arbsession.com/edelrid-swift-protect-pro-dry-8-9mm-night-green-base.html

These guys will do a tight eye sewn splice so you could do a dual connect adjust vario type design

edit: they’re out of stock despite what the website says

I just grabbed 7 feet of 8m cord from thr yosemite shop and it works great. Been using it for months now. Why does it need to be dynamic?

TaylorP wrote:

......Why does it need to be dynamic?

The last thing I want is to start (another) MP debate on this topic. There's been lots of discussion on fall factors on static ropes or PAS in the past. This is perhaps the quickest reference:

https://www.blackdiamondequipment.com/en_US/stories/experience-story-qc-lab-personal-anchor-systems-explained/

Update: That 9mm rope I linked above works well, but is a tiny bit chunky. The tether is easy to pull in but somewhat frictiony to release. I’m gonna stick with what I’ve got, but when it wears out I’ll try to find some 8.5mm.