I have brewed this 7+ times, did it three different ways, and whole berries are the way to go. IMHO You can mash them, however, they are a pain to rack underneath when they are fell apart. As the yeast eat the sugar in the berries they become very soft and evenb lose alot of there color. Also, Keep the temp down around 65F-68F ambient, this is to help control your ferment. So the answer is.......up to you. Its always up to the brewer but in my experience whole is the way to go. Also freezing the berries break the cellular structure holding them together, hence making them softer and juicier. Did I answer your question?