This is a bit 'broken telephone', but I recall reading that Scheiner supposedly played a 5.1 mix he'd done at a convention or lecture or something sometime in the 2000's. There's also this article from
High Fidelity Review (I'm not sure from when) that suggests he was in discussions to do so as well.
It would be nice if he'd join us here and let us know. I wish more engineers would read/post here, as it's a great way to build grass-roots support, and I don't think we're the type to chase industry pros off like they have at SH.tv. Anyone from Elliott Scheiner, Greg Penny, to producers, label execs, etc. could not only answer a lot of questions, but also get to know their target audience better, which is never a bad thing. I'm not asking them to post as prolifically as fredblue, but the occasional Q&A wouldn't go amiss.
Just to tie Robert Margouleff back in to this as well, you can hear the synthesizer he built for Stevie Wonder on 'Natural Thing', the first track of the Doobie Brothers album The Captain And Me, which has an amazing Elliott Scheiner 5.1 mix, as has already been mentioned.
As far as I know the story with Stevie Wonder is that he won't let anyone touch his master tapes - apparently everything that's out there now, the CD's, the HDTracks downloads, the HFPA Blu-Ray, they all come from safety copies of the master tapes. If he won't let anyone touch his master tapes, I think it's a pretty safe bet that no one's getting anywhere near the multitracks. I assume that's why you haven't seen a single bonus track or outtake on any of the reissues of any of his albums either.