I was in the same boat as you when i first used the knot. As everyone stated, tension is key. Check out "tackle advisors" video on youtube. He runs the line through his nails to get rid of any way, build up, twist, etc. in the line before he starts. Then he uses a method where the lines do not have to be tense because he is constantly pulling the line back while pinched between his fingers.
Also, a rizutto finish as opposed to a finish with multiple half hitches, has helped me tremendously. Whenever i used opposing half hitches, the knots eventually opened up after running through the guides. Not to say it doesn't work for some people, but i found the design of the rizutto finish naturally complements the knot since it tensions itself onto the FG as the line is loaded up. See "Hitchless FG Knots with Rizutto Finish" on youtube. The quality of his video is horrible, so watch it to get an understanding, then find another video on the rizutto concept.
Lastly, some people might think it's cheesy, but i have a knot assist 2.0 which has helped tremendously with the lighter lines. Obviously with light lines, you want to avoid too much tension which will make the line weaker if stretched beyond it's limits. It is not necessary, but it has helped me with efficiency.
Hope that helps!
