Yeah - I'm doing Higher Biology right now, and I think it'd be ok to crash. There's a lot of content to memorise, but you don't really have to understand it. It's quite straightforward though. Definitely have a look at some of the N5 content as preparation, but I hardly ever have to refer to my N5 knowledge for Higher, as it's mostly completely new concepts. I know someone who's crashing Higher this year as well, and they're finding it just fine.