Blu-ray content to a standard DVD-5 yielded

If the film is accepted at Cannes, they'll require either a 35MM Print, or a Hi-def version. But what exactly is Hi-def?
As recently as last year, this might have included DS tape, but with the advent of Blu-ray the quality could be much higher.
Our film with uncompressed 5.1 surround stems could weigh in at nearly 70Gigs. So the research into how to best compress the "Hi-def" version of the film begins, and I welcome your thoughts and comments.

The first tests burning Blu-ray content to a standard DVD-5 yielded some nice results. Using the just released Toast 10, I managed to fit several 2 minute clips that played smoothly, albeit with odd aspect ratios. Menu authoring in Toast is pretty poor at this point, a little worse then DVD Studio Pro, and I'm not much in the mood to build the menu in Motion and then import some snazzy graphics into DVD Studio Pro.
Luckily, our 7 minute film should fit on a standard DVD-R, but I have yet to add the surround stems. I'm also not clear whether Cannes will accept a DVD-5 authored Blu-ray?

Oddly enough, video post services in the bay area don't appear to work with Blu-ray yet. I've yet to explore Los Angeles...