I think Kerry Butler was perfect for Penny in Hairspray, but I found her Audrey extremely bland and not vocally powerful at all (but then again no one can really match Ellen Greene). I also listened to the Little Mermaid demo with her on it and she just didn't seem to fit. I thought of someone more like Sutton Foster for the role; very spunky with a clear pop belt. Sierra definitely looks right for the part in my opinion; I won't judge her singing til I see the show.