I just watched all of those bladder volume test videos ( Thanks mgardner!) and figured on a whim I would ask one of the cam girls that I follow on MFC to show me how much pee she had. This was without any preparation or desperation from holding.
According to her this is a 3 Liter pitcher that she used, so I did the math using the law of proportions. Based on this picture, she just casually pissed 1.6 Liters!!