At 145 i found a 151 SL to be a little stiff for me to learn on (others have no problem pressing, I did because,well, I've never pressed before). I could get the tip barely off the snow but not a whole lot. The Proto and SL have similar flex.
I went with an EVO which others have said have zero problem riding the rest of the mountain except the bigger features and bombing real fast.
i weigh less than that and im on a 151 sl...no issues pressing and im no pro by any means (the first time i pressed was with this board)