Well depending on how hard you push yourself, snowboarding in general can be dangerous. A 157cm board is probably going to be too flexible, and probably not damp enough. The only time height really matters is when it comes to stance width, and still that's preference.
You could use a 157, but it might not be very fun and you might find it difficult to use.
I don't really push myself to the limit if thats what you mean. I consider myself still a beginner. I only stick to the beginner and intermidiate trails whenever I go. Plus I ride maybe 2 or 3 days out of the year at the most. Last year didn't get any time in though.