I installed Sims String Leeches on the bowstring of my Mathews Q2 but noticed little if any reduction in string noise!

For those of you who use Sims String Leeches: What type of bow do you have? Where on the string did you install your string leeches? Did you put them closer to the middle of the string and the nock or out closer to the axles? I think the type of string and location on the string may be an important factor in the performance of the string leeches! Some swear by the leeches, while others curse them. There's got to be a logical explanation for this! Could it just be a defective batch of string leeches?