First off, hello all. I'm new to the forum. I plan on purchasing this. I just wanted to say that a potential solution to help in the prevention of the spectator sticking their finger in the bottle while they're holding it is to make sure you've given them an object to hold in what would be their free hand. (the bottle cap, a box of matches or something else that could pertain to the trick.) Make sense?
That's a good idea, and if you're doing it for a bunch of spectators, find someone who's already holding something in one hand. Good thinking.
I'd suggest you buy this if you're interested, it's definitely performable, and it looks incredible.