I think we will be getting 1st chapter if they are playing 55 minutes. If they have a 55 minute set with no 1st chapter, that means they'll play every single other song on the album, and maybe still have time for a cover. Not sure that's what they'd do.
If they play 1st Chapter, they have an additional 35 minutes, which is plenty of time to get every song in minus Biosfear and the bonus tracks. If they stall, Edguy-style, then they'll still get the best songs in (Sin, Alive, Glory of the Empire, Prophecy, Why am I Here)