Is not napping on RH only a Chabad thing?
I'm late to this conversation (was sleeping

). All I can say is that RYBs told me it is preferable to daven mussaf for the amud and sacrifice the inyan of not sleeping in order to do it. (He said something like, "How can giving up an inyan for the sake of the tzibbur be a problem for the Yom Hadin?") He did say to wait until after chatzos, so I did.
(Similarly, I daven mincha for the amud on Yom Kippur, and as a result, I don't have much of a neilah. My feeling is that it is worth it, and I don't hold anything back when I am at the amud - but I never asked RYBs.)