I must say azert84310 that your n20 inflation looks rather painful, either that or your balls have a real bad case of blue viens surrounding them. I hope everything is ok and that everything went to plan. Aside from all that, you look great and I bet it was fun.
Looks like some kind of tubing. I tried N2O and have had the same issue - keeping the gas in my sac. I would be curious to see what the best way to tie off is and what is the best stuff to use to tie off.