Following "the shape or form of chuppa":
Halachicly speaking, Chuppah makes Nissuin - the start of the formal obligations of both sides.
What is the minimal footage of a Kosher Chuppah? A square Tefach, Amah, 4x4 Amah? What Chuppah size would not constitute Nissuin?
Note, I'm aware of other approaches to Chuppah, but here I talk about the standard contemporary accepted ones.