Looks dead on to me!
Can you post a close up of your cables and how they attach to the spoiler, I want to compare them to mine. Thanks!
I found a stainless vinyl coated cable kit on amazon that had the little clamps so I could adjust the tension side to side to get them both tight and the uprights level
That's a great idea and they are clean looking when installed. I have seen a few railings done with them.For what it's worth I found this today looking for affordable aircraft cable turnbuckles. Stainless Steel Swagless cable end mounts and turnbuckles for railings. Much less expensive than aircraft turnbuckles and look very similar. Apparently they'll hold to the same tension as the size cable you use.
This is just one company that makes them.