I have a little data to share now on the tieout failure tests since I was able to borrow a cheap fish scale.
The worst case started deforming around 10 pounds and busted in the 15 range. The best of the ones I had done previously managed about 40 before breaking on a single attempt but repeated pulls to 30-35 would eventually cause it to go.
I did a few other combinations. I doubled up some GG and it held to the 50 lb max of the scale. I doubled up the loop and it held repeatedly at 40-45 but gave out at 50.
Then I made a single loop of the 3M 8959 that I had used on my previous tarp and it held 50 repeatedly. I suspect it would also fair better using washers since it's essentially high-grade strapping tape.
So what would I do different knowing this? Prototype #3 will likely go back to using 8959 for the actual connection point of the tieouts. However, it must be covered with 2120 to provide UV protection or it will disintegrate like normal strapping tape. GG could be used but it is not as strong as 8959, is heavier and it just doesn't look as nice. :) Maybe I shouldn't be so vain. LOL
While it's difficult to determine just how well the forces are distributed via the tieouts, you can at least guess that if you can accommodate at least a 3" section that it would take at least 25 lbs to break the tarp material based on the thread we had a couple months ago. So if my tieouts don't break until 50+ lbs, I shouldn't have to worry. Ryan's Storm Resistance article (when will Part 2 ever come out???) says, "Generally, moderately stormy conditions (snowfall equivalents of several inches through a night, or wind loads induced by 30-40 mph / 48-64 kph winds) can transfer up to about 40 pounds (18 kg) of tension force to guylines and stake-out points for most solo shelters." So I should be good to go there, but the article also states, "a significant mode of failure of ultralight shelters, especially those that employ low-stretch fabrics such as Cuben Fiber, is the shelter’s inability to be staked out tightly at high enough loads that induce a good distribution of tension evenly across all fabric panels. (emphasis added)" I think the saving grace here will be that the material does have a little give.
As an aside, one other point that I noted in the video but not here - the "catfish dropline" I got at Walmart held repeatedly at 50 so it would be suitable for some guylines. I don't know if it would work with linelocs or hitches though as I just tie a bowline on each end. But it's cheap, lightweight, braided nylon twine.