Finished the whip! It took a solid weekend and came out about 6ft + a 2ft fall + 8 inch cracker.
I'm pretty pleased with it overall, although I think the cord lengths given in the video were pretty low for me, I had to use 50% longer on the top layer to get it over the whole whip, and the lack of filling out from the inner layers means I have a nearly non-existent taper over the last 2ft of the whip, so if you are planning on following Nick's videos bear that in mind.
Went out to the park to try it this evening, it's surprisingly technical to crack, but when the timing is on it requires basically no effort for good loud bangs. Lasted about 10 mins before I got a noise complaint from a nearby house and decided to vacate
Pics will arrive when I'm in and have decent lighting as my phone camera sucks in half light.