I attemped to draw a diagram of a DUCAN LOOP and failed. I did a google search and here is a great set of diagrams. It also turns out the DUNCAN LOOP is also a "uni knot" or atleast thats what this site says. I always knew it as a DUCAN LOOP.
To DeeJay in my above post I stated a loop when not using a split ring. If you use a loop there is no controll over the matter. Also there is no need for the loop. I left out what knot to use on a split ring, an improved clinch will do. If you tie this exactly opposite the gap you should not have a problem with it moving.