Well, we know for sure that both SuperSession & the BST stuff was mixed into 5.1 by Al Kooper, but is being sat on for some inexplicable reason.
I have these in QUad too - including a version of SuperSession clocking in at 75 minutes run time too. It's GLORIOUS!!
I also understand the entire Led Zep catalogue has been done to 5.1, again in the vaults for the forseeable future too, likewise Deja Vu.
Blind Faith would be terrific, but do not hold your breath as I suspect the multitracks are dead & gone a long time back.
Electric Ladyland is possibly 4 channel anyway - it certainly decodes beautifully & the masters are allegedly marked "Do not adjust for phase".....or so says the legend.
OH GOD!! Neil, this is SO depressing to hear
Warner.. what is wrong with you!?
Rhino/Warner pulled the Stephen Stills DVDA! they pulled Quadio after 2 releases! they've never released CSNY's Deja Vu in 5.1 (even though its been mixed into surround, it's begging for a DVDA!).. they released a Live set of Zeppelin in 5.1 DVDA, when the whole back catalogue as you say has been mixed into 5.1!
and they never released their 5.1 mixes of VM's Moondance, Rods' A Night on the Town or PS' Graceland..
So stupid! SO sad