Funny I am writing this - I was at a job today and this guy was wearing a Dead shirt and of course we started talking, and I asked him what shows he remembers the most. His first response was RFK, and I thought, cool, and was incentive to hear the famous RFK Dark Star. Haven't listened to it in a while and I don't remember believing there was anyone but the Dead playing. So I'm listening to it and all of a sudden I hear what sounds like an Allman Brothers rift, and my first thought was heck - that is no doubt Dickey Betts playing. And I also noticed the keyboards sound different than Godshaux, and thought could it be Merl? I later read your comment that Merl Dickey and Butch may have been in the 3rd set, and so I had to listen again. Then it hit me - there are 2 drummers! I wasn't there, but if they played in the 3rd set, they sure as heck must have been in the 2nd set too.
Sincerely Gabe