Its a fun project thats for sure.
With double of the plastic line how firm is it? One of the reasons I don't like leashes is because they feel unatural when holding the rod due to tension.
Anyway on mine I have them double shrink wrapped. First, I burn off each end of the plastic line to round off the sharp edges, then I add a small shrink wrap over both lines...all of this to protect the transition from the plastic line and sheath to sheath only.
Finally I add another shrink to cover the knot. Seems a bit excessive but its really easy and only takes a few seconds.
Pic shows the shrink wrap covering the transition
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