Hi and welcome to the forum. By sand training, I'm guessing you mean volleyball. If you're doing 2 hours 3-4x a week on top of the crossfit workouts, and ~7hours on Saturday, I'd say you could definitely benefit from higher carb intake. The book (Primal Blueprint) and a lot of the blog posts concerning carb intake are geared towards people who are less active and have weight to lose (not you). You can get get Primal carbs from sweet potates, winter squash, even white potatoes and white rice can be acceptable. Lately there has been more acceptance of higher carb intake int he Primal/paleo community. Just keep away from the grains and seed oils and you will be fine.