You're so right about Guercio ... in addition to the flat, muddy sound, my recollection is that those first couple albums were in mono, at Guercio's insistence and despite the fact stereo was pretty commonplace by then.
Can't imagine how a man of Guercio's dubious talent made it as far as he did ... he was even given control of and directed a major motion picture. 'Electra-Glide in Blue," starring the second best-known acquitted murderer-actor Robert Blake. If you're ever feeling particularly masochistic, throw it up on your Netflix queue and give it a look. I don't think I've ever seen a more convoluted mishmash of storylines, scenes and shots. The thing makes virtually no sense at all.