RE: Please help me with the choice of the right Kombat volumes!
I don't think you should be afraid of the width. The performance of a board (including control in chop) depends on many other factors too and the Kombats are designed to go really well in chop. That said, boards size is always a compromise between effectiveness in light wind (big board) and control in high wind (small board). At 90 kilos I think he will manage the 107 quite well though, but since you already own the 96, the best thing is to try a light wind session on that board before investing in a new one. New boards are nice, but even if you decide to get a 107, getting some experience on how a 96l board handle light wind is still a good thing.