Hi Mark
I wouldn't use 10X if I was using a friction knot. It's no worries if you're using another form of knot that isn't dependent on friction but I would find a softer leader for a friction knot. You will find guys who will tell you that they use friction knots on very hard mono leaders and even fluorocarbon without any problem but it's a risk I am not willing to take. A frction knot is dependent on the braid "biting" into the leader itself. It will bite into very hard mono leader but it can also slip more easily. Fluorocarbon is such that braid doesn't bite into it very well at all. In such cases, it is the tightness of the knot and the burnt end holding it together. Once it starts to slip, its a goner.