Deep, totally slack water that would not allow any sort of swing presentation at all.

You slide the plastic tube up your mainline and then grasp the knotted piece and then slide the plastic back off the mainline ... you then pull the ends of this stopper tight and you can slide it up and down your mainline whatever depth you like w/o having a huge long leader when fishing greater depths.

I understand your one method reasoning ... BUT, adaptation is the key to catching lots of fish all the time, not just part of it