We also have a 24" pizza in our shop.
Couple things i should mention. First, i have noticed that even though the platter is on the wall with the rest of the sizes, people dont realize just how big that monster is until its cooked and sitting in front of them. Also, that one 24" pizza takes the place of 6 14" pizzas in our oven. we even have to take the stops off the end of the conveyor so that it can bake completely and evenly whenever we cook it. If you have dine-in service and small waitresses, chances are that they will be too scared to carry it to a table for fear of dropping it (some of mine are). Also, we do ours dine-in and carryout only. It is too big for us to deliver. We havent invested in the delivery bags big enough to carry them as we dont really sell enough of them to make it worth the expense.
However, for a positive aspect, one of our franchises started the whole 24" pizza thing with our chain. He has made a challenge for it, which helps him push it. The rules go a little something like this… 1 entire pizza, 1 person, 1 hour. If you can eat the entire thing, crusts and all, in one hour without urping, then he will give you $100, the pizza free, and $5 for each failed attempt since the last successful attempt. Manager picks the seat, no one else can even touch the pizza, or you are disqualified. You cannot leave the room, although you can get up and move around near your seat if you wish. This can create a lot of hype around your college when you get someone to win it. I cant say for sure, but i believe he shelled out over $500 to a person once that had won it.
Just my thoughts…