To make baked ziti for 50 people, use a baked-ziti recipe and increase it. Take the number of people you want to feed and divide it by the number of people a recipe says it feeds. This gives you the number you need to multiply your ingredients by to achieve the amount of food you require. In this instance, divide 50 by six, which is the smallest number of people the FoodNetwork.com baked-ziti recipe feeds, and you get approximately eight. Multiply the ingredients in the recipe by eight to achieve the correct amounts.
Preheat the oven to 400 degrees Fahrenheit. In a large pot, boil the 8 lbs. of ziti pasta in salted water until it is al dente, or not completely soft. With this amount of pasta, you will need to use a few pots at once or cook the pasta in batches until it is all cooked. Drain the pasta when it is done.
Oil the large aluminum trays and pour the cooked ziti into them, putting an even amount in each. Mix in the 28 cups of tomato sauce, 2 cups of the Parmesan cheese, the 2 cups of pecorino cheese and the 4 lbs. of cubed mozzarella cheese. Mix in black and red pepper to taste. Top the ziti with the 4 lbs. of sliced mozzarella cheese and the remaining 2 cups of Parmesan cheese.
Put the trays into the oven. You will have to line them up two next to each other, using two oven racks. Cook the ziti for 30 minutes, or until the cheese on top is bubbly and browned. Rotate the trays halfway through the cooking time, so they all cook evenly.