This has been kinda rumbling around in the back of my mind for more than a year, and now that Homer updated MMH so that SACD channel remapping was possible, I finally did the swap and had another listen.
I actually liked it better with the channels reversed, but I think the way it is on the SACD (bass and drums in front) is correct. The reason I say this is because pulling it into my DAW and checking it out on headphones, the front pair (bass and drums) has a lot of stuff mixed dead in the phantom center including the bass itself, and a lot of the drums. The rear pair has virtually nothing mixed to phantom center, and the vast majority is mixed very wide, often to the point of being hard left or right.
For me this is telling, because RtF was a (single-inventory) SQ LP release, and one of the cardinal rules is that you can't have anything in the rear phantom position, because at best the information disappears in mono, and at worst it can create pure vertical modulation during LP cutting meaning the master would be impossible to cut to vinyl. I actually really wanted the opposite to be true, that the fronts and rears were swapped, and that there was no phantom center channel information in the bass & drums fronts, so I could have my murder mystery 'see? they're reversed!' shocking reveal, but alas that isn't the case.
Regarding the harmony vocals, what's going on there is a number of diagonal pans and stereo pairs that attempt to make the vocals what we'd now call "immersive'.
The front left and right give you a stereo spread of the high and low harmonies, with reverb.
The low harmony is placed somewhere near 'quad center' by suspending it between the front right and rear left speakers, akin to what Don Murray did on the quad mix of the O'Jays Ship Ahoy album, similarly suspending the bass vocal diagonally on a couple of tracks. The same thing with the high harmony between the front left and and the rear right, pulling it out into the middle of the room. The net effect is that you're surrounded by stereo pairs of vocals (FL + FR, FR + Rs, Rs + Ls, Ls + FL going clockwise) plus the individual vocals put in the middle of the room. It's a pretty clever engineering trick, and not one I've seen employed in any other quad mixes that I can think of.
