Adrian
I suspect, as there is no evidence that I seen or heard of that boilie stops harming fish when swallowed.
The digestive system of a fish is very primitive in comparison to higher animals. Fish take in lots of rubbish over their lifetime and rarely do they come to any harm through it.
If you are concerned about it why not make the stop permanent on your hair?
I wrote a piece on a rig only the other week on how to do it. The rig is a sliding hair but it can be modified so it doesn?t slide.
click here.
You could also use the Korum stops as well.