Remember the power of ONE for a light, crisp batter. I use any kind of summer squash I have growing in the garden -- zucchini, Yellow Crookneck, Patty Pan, 8 Ball, Papaya Pear, Sunburst, ... . IMO, the best size for frying is when the seeds have begun to develop but before they've gotten large and hard. The immature seeds add depth to the flavor. Cooking time will vary with the size of your frying utensil.