Actually the comments about Brittens open bike airflow reminded me about the current generation bikes airflow,
Kawasaki H2 and others split the air and create boundary layers, H2 and H2R pick up air in the front and ducts it to the fairing cutout near the hands , and directs air from the riders seat to the undertail
a huge sail to the wind is obviously not the only way to get the air around the bike and rider
