CompuServe Messages

The Stack data is not really "Undo/Redo" (though it can be used for that). Each object has its own stack, and they're stored in the scene file. As to size, I haven't done any benchmarks yet. You'll have the capability of collapsing the stack on any object, which will eliminate the entire construction history of the object. (Of course, this will be a one-way operation. Once you collapse the stack, you can't go back and access the applied modifiers.) – Jack