Double elimination is just that, you must lose 2 times in order to be knocked out. Even if the 17's lose, they still must lose again. That's why the AABC bracket already has them moving on to Saturday night. AABC is the most fair bracket out there and it gives no one an advantage.
In looking at the bracket, here's how things could work out IF the 17's lose:
Since the 17's already have had a bye and no one else has, they would play in the first game Saturday regardless. Then the other two remaining teams would draw for the bye. Who ever gets the bye, would advance to the championship game.
If the 17's win, then it's a mute point and either the 18's or Mustangs would have to beat them twice on Saturday.
See, it's not that hard at all. Plus I've been around these tournaments for over 30 years so that helps too!