What would be the best arrow length for a 75lb drawback Buckmaster PSE compound bow?

im a noob at technical archery statistics. i read somewhere that 'usually an arrow the same length as a bow's drawback works best.' my bow's drawback length was written on it as 31", so i bought 31" carbon arrows and they seemed to work fine, maybe a little shaky on take-off. and then i noticed that my arrows were sticking out a good 1 1/2-2 inches from my bow, so i got some 30" arrows. but these are totally retarded. everytime i let fly them i can see the backends of them flapping back and forth on their way to the target, very inaccurate and sometimes veering completely off course. im sure getting a bow with a weaker drawback weight would solve my problem, but i like my bow. any other suggestions? should i go back to 31" arrows or get an even shorter length?