Very enjoyabe disuccion of a great Rock'n'Roll album!
Regarding the "Dennis-on-Surfin' USA"-discussion: I only knew the rumours that Dennis wasn't on the track but all the speculation around it was new to me, so I may be overlooking something. But I just listened again to the demo (released a.o. on "Hawthorne, CA") and there is a certain difference between the demo-drums and the master recording. The demo version (of which I don't know when it was recorded) has the drummer hitting the snare on the "4" on some of the "just bassdrum" measures. This is the way Dennis played on live shows. The master take though has only the bassdrum on these parts on all 4 beats. So my guess is Dennis plays on the demo, someone else on the master.
I also wonder if the slight lyrical changes from demo to master take come from Mike, hence his co-writership claim.
https://www.youtube.com/watch?v=mslLZD_8RUgEDIT: Not sure about the intro to "Surf Jam". Sounds like two voices on the left channel, one on the right. My guess it's Brian and Mike left, Dennis right. But if this wasn't "live" and overdubs did take place, I'd say Brian and Mike left, Mike right as I don't think Dennis would call on himself. His and Mike's voices could sound similar during the first years from time to time.