Declare the board. If you are in the states for more than 5 days, you are allowed up to $500 in tax free purchases. Duties get real bad when they are shipped because of all the "processing" fees. If you are just crossing the border with it, it wont be bad, and as I said, if you have been there more than 5 days and declare it and it's under $500, you wont pay any at all. Worse case, if its a couple over, you just pay GST on it ($20-40) (had to once when I had $700 worth of clothes and declared it all).
In my opinion, it's just not worth getting caught. Not worth the risk for $50 of something.