Sadly I can only give this an "7". I really wanted to give it more, as 70's R&B is my jam and this is such a great album, but the mixing issues are what they are.
I was not familiar with the album other than the radio hits (of which there were FIVE), but the rest of the tracks are all solid early 70's R&B fare. An easy "10" for content.
But the mix is off, as already mentioned often here, for whatever reason, and it diminishes the listening experience. Personally, I think it's mostly just the choices of the original quad mixers. I don't find the Front Left to be too quiet, but on at least some of the tracks, the lead vocal is panned about 75% to the Front Right, so it gives that impression. Whether that was the choice of the mixer or a mistake they didn't catch, we will never know.
It does also seem that the Rear Right gets louder as the disc goes on.
Whatever the cause, the result is a less-than-stellar mix and on top of that, it's all a bit muddy sounding. I haven't A/Bd it with the stereo layer (maybe that sounds just as muddy too?) but it's all unfortunate as this album deserves better, IMO.