My quick thought on Darlin as a deep cut...I have never heard it played on the radio before! Perhaps in England and other places it gets played, but I haven't heard it on the Texas oldies station. Interesting that it was higher on the charts than God Only Knows which does get regular air play!
I heard it on UK radio in early '68. In those days (and a while before then) I played everything (on the piano) with a left-hand pattern that was almost invariably twice the bass note followed by twice the chord. As in "Darlin'"----and I remember what a joy
that was to play. In fact it played itself. Yes, it was all over the radio. Anything Beach Boys was big news in the UK, all the way into the early '70s.