At a lot...like...a lot. Get dirty with it if you have to. Have him eat 2 frozen pizzas after practice #2 with a couple cuts of pork chops/steaks/fattier meats for the kcals. Drink a protein shake with a scoop or 2 of protein powder, couple tbsp of natty peanut butter, fruit all blended together between prac 1 and 2 with a pb & j or two. Big omelette and oats for breakfast. Answers pretty simple really, he just needs to eat enough to match his energy expenditure for the day. And that number could be pretty damn high.