152 is perfectly fine.
it's funny you say it's too stiff. i have the later versions which are even more stiff than yours, and i think mine is ridiculously soft. how soft exactly do you want your board being?
anyway, if you're falling on your ass, it's just that you suck. no offense. it's not the board.
i'm not sure, but everytime i try and press it shoots me back down because i don't have the leg power/weight to keep it pressed.
but i've thought about it and would 5cm less really make that big of a difference?
2010 152 LibTech Skate Banana, 2010 Ride nRc Bindings