another thing that we need to consider in an ACR (i'm currently building my first one.) is pacing. an acr may take up more actual time than say an ace assembly. but an ACR is pretty much solid magic from start to finish hard core, non stop magic. whereas an ace assembly you gotta set up the packets etc.
so the key to a well timed acr is the smooth flow between reappearances of the signed card. while at the same time maintaining a steady build of drama, suspense, all that stuff.
(i just finished this section in strong magic right before i read this thread, it inspired me to finally put an acr together)
(definitely get strong magic.)
Yes I have heard many guys talk about practicing to music to get a good pace.