I am actually making a giant cupcake and I have a paper mold that is about 6.5 inches and 7 inches high. I am completely familiar with the mechanics of how angel food cakes and chiffons work, I just would like to know what the largest cake pan size I can use before I really NEED a center hole.
The answer, like most other things in life, is: "it depends". Angel food cake (and chiffon) can be very sensitive air pressure and humidity. You will find that on rainy days, the cake will rise higher and therefore have more of a tendency to collapse on you after baking. There really isn't a hard upper limit on when you'll need to use a tube pan.
That said, you might be able to get away with a 7-inch angel food cake if you do it at a low enough temperature and you're careful not to try baking it on a rainy day. You probably wouldn't get away with that using a 9-inch pan on any day, though. All you can do is try it and see what happens.