Would a different size/shape fin help?

Hi, don't know if anyone can help me, I am a 85Kg recreational sailor using an 11m severne overdrive on a F162 with standard fin. The sail felt fantastic on my F159 and thought I would get earlier planning/better handling from the newer SB but this is not the case. The board is a real handfull and just wants to rail up when well powered up going off the wind, I have been offered a Deboichet 68cm R13 soft, would this help or even work with this board? If not can someone please recomend a size and rake compatible that may possibly help.

Thanks in advance.