Flourocarbon is notorious for fraying at the knot when not lubricated (spit). The friction of the knot being tied weakens the line. Also try tying it with the trilene knot for your test.

You can also try using super glue on your mono to flourocarbon knot or use the loop to loop method. Mono to flourocarbon has been a hot topic for flyfishermen making there own leaders. Let us know your results

Tight lines

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Marty
www.steelheader.net
marty@steelheader.net