I completed the strength testing on the soft shackles. I tested both styles of soft shackles made from 1/8 inch Amsteel. To get a calibration point I put a straight section of Amsteel between the two soft shackles. Just to make it interesting, the straight section had a brummel eye at one end and a straight bury and stitched eye at the other. The test was made and the Amsteel broke in the middle away from the splices. Neither soft shackle broke. My test setup had 100:1 mechanical advantage and I had to pull almost as hard as I could to break it. Incidentally, there were no grommets on the eyes but they still held.
So, while I didn't actually test the ultimate strength of the soft shackles I did verify they are stronger than the line they are made of. For my application, that is enough and that was the goal of my test.
I now have 6 web pages devoted to soft shackles including one that has a video of the test. I was amazed how hard it was to break the 1/8 Amsteel.
http://l-36.com/soft_shackle_intro.php
Allen