Presuming this is not an english kip although I'm sure you need one after how hard they work you ;)
I'm not really doing them right now, but I could do 17 strict ones before my shoulder injury. I couldn't do the kipping ones, though. Finally figured out it was because I was too tall to keep my legs straight at the bottom. Need a higher bar.
Yes, Rob can't really throw himself around on the bar like I can either! It makes a big difference. It's a strange situation, strict is easier for technique but requires much more strength, the kip requires less strength but more technique.
Today I can't move at all on my bar at home, arms very sore.
Try it with your knees bent. Pretty impossible.