I love Brenno's reply, but technique will help. If you keep you feet slightly staggered (surf stance) and closer together (closer to the imaginary stringer) you will be able to adjust for the fore/aft rock and you will stop creating so much torque as you rock from side to side. (I have a 7'10" minion and am 6'3" 88 kg.)
It is worth it when you get on a wave
I am no fin expert but I suspect they would need to be a foot long before they would begin to help