I've been using XTP candy striped rope for years now. I use the slower B-53 knot because I hate sudden "skips" on my descents. I have experienced knot creep a few times. The creep is usually slow, but any creep- uh- gives me the creeps, and I respond with a vigorous upwards tug on the tail which stops that nonsense and brings my internal chemical reactions down to a tolerable level. I have never known the Blakes to create a free fall situation. A safety knot as backup down low on the rope might be a good idea until you regain trust in the knot. Like you said, we always tie a safety knot for the kids. Let's not forget that it is that same kid in a grown up body that gets us into the trees.