congrats on the gnu RC.
I have a 154.5 with a size 10.5 K2 t1db. I dont see any toe drag though. another thing is if your boot have srinkage tech, then you may be fine with 12 on a 157.5 rc. one thing important is that if you centered your boots before you worry about toe hang, and also just tweak 3 degrees off your binding settings may change something, also try a slightly wider stance?
i think you can get away with a pair of 12 on 157.5 but again, please tweak them before making any radical decision