Ok, that was nuts. I'm already thinking why you never see anything like that with stunt pilots.
It's got to be the power to weight. Most ultralights have 50-100 hp. I had one with 53 and that thing would never be able to pull out of a stall like that. I think you'd need at least 250-350 hp to do that. Then I think the plane would fall apart.
Also I don't think a human being could remain conscious through that.
Anyway, that was amazing and took a lot more skill than most would realize. It's not like driving. There are multiple axis and forces to think about. This guy has earned his spot as #1.