Man rugby 7s is tough. Tons of sprinting. You are going to want to eat a lot of carbs - but just as importantly lots of food. It's hard not restricting your calories when you transition to primal eating just because you stop eating grains, rice, sugar etc -- stuff with lots of energy that is quickly consumed and doesn't fill you up. I would worry more about not consuming enough calories/carbs than consuming too many. Personally I find it very hard to overeat on Primal/paleo.