I finally moved away from my old PVC stick, and built a similar design to the Smooth Operator (aka Fiddlestick). Now to test it out and try some knots. For each test, I climbed up and down the rope and put 2 people on it. Then pulled the stick out. I did this 3 times for each knot. No gauge used. How hard was it to pull out? What kind of twists left in the rope on release? And, how easy could it fall out prematurely? First knot: a stone knot derivative. I tied a stone, then added a twist before setting it. This was the easiest to release. It also set the stick at a ~45 degree angle due to the nature of the knot. This setup seemed the most risky for a premature release. Second knot: stone knot. This took some effort to start the pull, but then released very quickly and popped out. There is also a trick when tying this knot so you are left with no twists after release for a clean pull. Third knot: constrictor knot. This was really hard to pull. This knot really cranks down! But I was eventually able to get it out (but pulling with no corners, or other obstacles). And that "Smooth operator" song by Sade seemed to hum in my head during all these tests.