What Size Snowboard Should I Get?

With a smaller board size, not saying yours specifically, the width of the board will get smaller and smaller, so you might get an half inch or so of toe drag which might have some affect of your riding. You'll also get more toe drag is your binding degrees are closer to zero which means they'll be more straight and have more drag, but more comfortable position is better than toe drag, that was just a fyi. I'd personally recommend looking at new bindings that'll fit a different board brand that'll have 154s or so in"wide" versions, especially with size twelve feet.