Yeah, thread stitching on cuben can be a real problem. Especially with 30mph winds, and the potential for snapping, or flapping fabric (impact) adding stress beyond what is normal. 40mph it becomes down right damaging.
One of the big factors IS the impact. Wind stress can load and unload rapidly, imparting an impact "moment" to the fabric. Any fabric is subject to this. Alleviating it is simply a matter of using elastic strapping or elastic guy lines or sumply an elastic hair tie on the loop.
The low stretch nature of kevlar, carbon, Dyneema, or spectra fibers used in cuben materials is at odds with the fairly elastic nature of the plastic films between them. I anticipate that any threading over the fibers will cause a stretching of the material between them. Hence, as Ryan's photo shows so clearly, elongated holes where the stitching has damaged the "body" material as it stretched, locking around the fiber (wich doesn't to any large degree.) This will cause some stretching around the fiber, but, since it was not damaged, it remains intact, but thinned. Since it is still bonded to the cross grain fiber, it doesn't spread. The result, if allowed to continue to failure, would be a ragged edge starting at the origonal score line. The period of the failure would be the strength of the fibers, and the skin. Indeed, I expect at some degree of stress, you could get a "creeping" tear, it will fail in slow motion as the body picks up stress, stretches and finally tears, then the next one does the same. Generally, sails are directed fibers, ie, directed stresses to the points of attachment. Fibers are laid to pick up these stresses directly. We only adapt cuben cloth to tarps and packs because it is light. Sewing is not the same.
Stitching cuben would not be my first choice for construction methodology, therefore. The damage to the body skin will always dictate the weakest point at the seam because it is a combination of the skin and fiber that is the overall strength. I think this was pretty much the result of the "bucket" test. Once you hit the stress exceeding the strength of the film, it may hold together, but you get some elongation of any stitch holes, till the stress can be distributed among surronding material to compensate. As is seen in Ryan's photo. This can be looked at as a fail at that point. You have exceeded the strenght of the film, it is stretching. I would call it a mid-failure though, because you still have a compensation reaction, among the surrounding material. For a sail, this is bad, eventually fatal. For a shelter, not necessarily fatal.
Stitch length becomes important in distributing loads. One in every other "box"? One in every 3-4 "boxes?" Anyway, it will lead to a weakness, never a way to totally compensate, again, going back to the bucket testing.
Really, bonding, with appropriate glues, is much prefered. I would suggest simply bonding heavier material at the tieouts, pole pockets, etc. Say, 1.1ounce materal to .53 material for stitching. Cutting and adding lapped triangles should work, OK along the edges for guy lines and pockets. Gluing on patches should work for other tieouts. Generally, stitching should be avoided for maximal strength. I think of cuben as reinforced plastic. Not as a single material like silnylon, though ripstop has similar characteristics. Multiple layes of fibers going different directions would help a lot. Fibers in the same direction probably not much. Totally eliminate the problem? Probably not.
Anyway, I don't have any real experience with cuben, soo, I won't say more. Just a few thoughts...