Is this a very limited release or why not just give it a few weeks and you'll get seats without any trouble?
For the theaters near me, 70mm IMAX showings even a few weeks out still had only crummy seats. Also, I'm impatient and want to see it soon!
There's only 25 theaters in the US that even have 70MM IMAX projectors, so it is indeed pretty limited.
The IMAX screenings are pre-committed to future movies -- it might be the case that Spider-Man takes over in two weeks and the window for The Odyssey is closed, even if more people want to see The Odyssey in IMAX than Spider-Man.