The shackle should never be a replacement for the commercially tested quick release that comes with the bar.
In three years of wave kiting I've only had the shackle release when I've pulled it. It should never be a replacement for the commercially tested QR on the bar, which is what I use if I want to ditch the kite. You must test that the end of the chicken look will easily pass through the shackle - some older chicken loops have large rings on the end.
As I mentioned I've only had safety problems when using a carbiner because it caught lines.
Here's what I've been using. Not pretty but it's worked well. Two pieces of PVC pipe, one inside the other, some good quality rope and a shackle.