I his case, i would go for 133, but he is under 80 kgs and he want a board very balanced in HW too. Is his choice, not for me.
In fact, im over +80 kg and will go for 155 which let me cover the 6.5m -- 8.7m sail range.
I initially thought Fut155 would work fine with 7.5m-8.7m and And leaving the small board (122ltrs) for 6.5m sail..... but i tried 6.5m with Fut155 and she passes through the chop pretty well.
Over 8,7m i will use FW + 11m.
Im happy to find a board like Fut155 with such wide wind range, let me use 6.5m 7.7m and 8.7m (2 masts and 1 boom) Allowing me to downsize my quiver and adapting to 90% of my spot conditions.