According to snowboarding "law" it has too small of a waist for 12's....the 157 is 25.3 and with the larger boots you would want something at least 26. Which is why they have the Proto CTX where the 158 has a waist of 26.4.....BUT...that difference is only 1.1cm....for us 'mericans that's 0.4" which isn't really anything and if you were able to, which is see you currently aren't, I would say take it out for a test drive because it would really depend on your stance, width, and angles.
I am a little tempted into getting it though...what kind of condition is it in?
I always wanted to ride it but Leo has those girly medium bindings on it and it always seemed too much trouble to put mine on to test it out. Now I wish I had.