Oooooh man, that's quite a brutal one! Especially the second rotation of each group truely burns out those abs, when they were already under tension for so long from the static hold. Highly recommended to everyone who wants to do his/her core a favour. In my eyes it's definitely a 4/5 rather than 3/5 :)
Small success for me by the way: To get the blood flowing before the workout, i just tried to do as many pushups as I could in one set and I reached 50, before my form gave up on me. It's been a pretty long while since I was able to do 50 pushups. Once again big, big, BIIIIG thanks to K&D!