They take a little thought to get the most out of them. Booming them out helps, but there are other things that are just as effective. One of them is to take care with spreading them out. All similar devices (like the Magma stopper), create some flow as they pull the water towards the surface. The unit then has to drop back through that flow on the down stroke. After a few cycles, they create an uplift current stream, reducing their effectiveness. Even still, they are effective.
If the Rocker Stoppers are spaced as close together as shown on the packaging diagram, you can't get the full effect of each stopper. If they are pulling up through a 6" cycle (like just tied off from your gunnel), the uplift current created means that they should be spaced about 24" apart. Stringing 5 close together is probably less effective than 2 spaced further apart.
The other thing that really helps is modifying the Rocker Stoppers to help them drop. A couple extra holes in the "peak" of the hat helps them sink faster (as shown in the picture). I then added "reed valves" to help them drop even quicker. Because they dropped easily, that allows the use of a little 2# cannon ball as the weight (which then tucks into the hat for storage).
For a $50 investment, they are light weight, quickly deployed, quickly retrievable, stow easily in a 2.5 gal. bucket in the lazarrete, and therefore have many advantages over the Magma $tainless $teel $toppers. The Magma system might actually be 23x better, but fortunately I don't need that.