Go to your local hardware store and pick up some slick polypropylene to test the loop via slack repetitive shaking. This loop is one of the first tied by people who are trying bends as a loop. However the (Double) Carrick bend form carries itself loosely, which may be the reason for its mediocre security. It fared better in the natural fiber ropes back when manila fiber was king.
Tied as a loop, more problems occur. If you alternately pull legs to simulate swinging or rotation some unsettling things can occur. You may also want to try ring loading the loop in polypropylene, so that you make the loop act as if something is trying to expand it. You may be unhappy with the results.