I am worried about that. If the seizures happen, maybe I will overturn tank, and make the tube slip down. I must succeed.
I have no way to alive unless someone can donate me 500 dollar every month so that I can go on my education. (just kidding)
What I've read hypoxia doesn't give servere seizures but can after losing consciousness jerk and twitch the body. This is why some use straps or an appropriate chair which will stop the user of falling down. It's also advised to strap the cylinder down since it could damage regulator/flowmeter if tipped over.
Are you using exit bag or hood? I ask since your concern about the tube falling out, that will not happen on a EEBD hood since it's firmly attached to it.
Whatever your decision I will support it, but upon reading your last paragraph are you sure there is no other solution?
(Sorry for being a toxic pro-lifer)