Thanks for your replies guys. I am still pondering. If I didnt have a SP I would definitly be aiming for the BP. I think I need to play with the fins a little more on my SP and go for something a bit more performancy to eliminate getting something similar with a few tweaks. I am now about 80 % sure that the Potato-nator should be next purchase for those chest high + days.

NN66 we are about the same weight I am 6ft 4 and looked at the 5ft 11 and the 6ft SP side by side in the shop. The waves we get here are 60% gutless and chest to shoulder high and the reste of the time can be good and overhead. I plumped for the 6ft thinking the 5ft 11 would be too short for my stance. I am intersted in your fin selection though. I have struggled to get a happy medium. I first tried the SP with Simon Anderson quads in and it felt too slidey in anything big and lacked drive. I then opted for MRTFX fins in the front boxes and a set of standard m5's in the back, This is what i am currently riding and its great but on the bigger days the board seems to be glued to the wave and can getting it up on rail can be sketchy. The attraction of the BP was the 5th fin a Knubster would fit nicely I think.

Will report back. Again thank you all
Happy New Year
CiSurfer! :)))