This is a video of crazy person Will Pemble's journey to build a one-man roller coaster in his backyard (which is actually his fifth homemade roller coaster because everybody needs an insane hobby). The first part of the video focuses on his initial build of the coaster, then the second half deals with the trials and tribulations of trying to add a barrel roll to the ride. After adding the barrel roll, Will has been the only person to ride it (and only once) and says that it's "borderline not safe", which, based on the video, I would argue is actually definitely not safe. Still, give me six beers and $5 and I'll ride it with my hands up the whole time.
Keep going for the whole video, and remember: you don't need crash test dummies if you have beer and idiot friends.
Thanks to Clark, who agrees you don't even have to tell anybody to hold your beer when you're confident enough to hold it yourself doing whatever it is you're about to die doing.