Owing to popular demand (well, Roger), here's a photo of the revised zip-stop on Katabatic's Bristlecone bivy.
As you can hopefully see, the material at the end of the zip has now been folded over a couple of times, and sewn under the rest of the pertex for reinforcement.
It's a subtle change, but hopefully an effective one.
And if a photo of a zip stop isn't geeky enough for you, here are a couple more of the tie-out loop and the stake-out loop. May the nerdgasms commence.
All I need now is an opportunity to try it out again...