the sl4 is much better than sl2 for this board. sl2 spin out often. with 44 you can get early planning and nice lift on flat water with your 7,8. 42 better for your weight on choppy water. for the 7,2 40 cm is nice but in overpower condition i would prefer 38 for you in the iSonic 111. i dont know the tech and vectors.
i hope its help,