Well! My little question has certainly taken off! I want one of those 8-cup pyrex or fire king cups now. Best idea ever, to make your pumpkin pie mixture in there, then pour it into your crust which is already in the oven.
But it is true, some will still spill, but it will be less and it won't be all over the floor.
Because I was so late with everything, we ate the pumpkin pie (unbelievably tasty, made with winter squash from my garden on a graham cracker crust) at about 4 PM. I guess that's not really a disaster.
Many thanks, kids, for your input. I learned something today. That it's not only me that has spilled pumpkin mixture all over the dam place...