Here are some rough polars from a run on my smallest front wing (570cm2 x 80cm) on a good day. Some angles are a little bit faster due to the influence of turning at speed.
My feeling was that until 90° or so a smaller foil would be faster. At these angles your riding style is closer to dynamic soaring like a seabird. I feel a larger foil would only help if the angle is above 90° ish and you’re no longer using bumps as the primary source of energy.
