The experiments are over. I have had two straight delicious, non-leaking perfect coffees, not too hot or cold, no leaking, no dirty looks from the cashier ladies, no defective lids, and yet, no winners.
One thing I have discovered, though, is my co-worker who sits behind me has won 4 times out of 10 on large cups of coffee. I'm at 1 out of 11, for medium. So bigger is better.