I don't remember where I read it, but I seem to recall Giles Martin making some comment about not mixing anything pre-
Pepper into surround given the limitations of the source material. As we all know though, effective surround mixes can be done from something originally recorded on 4-track. Steven Wilson did wonders with the first Jethro Tull album. (So if anybody here happens to be personally acquainted with both Giles and Steven, please pass Steven's phone # along to Giles so Steven can give him some lessons, LOL.
)