Against the wind

[masonspappy]

In Blender you could probably do a wee bit of scultping on the sail to puff it out a bit. Not too much or it will distort the image mapped to the sail object.

[El Kabong]

El Kabong ( Is your name from the cartoon? ) I think your the only one  to say anything about the helmet. For some reason the top panel of the sail has no bump map............I know it looks too rigid for a sail. Suggestions?

"Olay! KABONG! ...and there's more kabongs where that kabong kabonged from!"   ...so, that'd be a yup.

https://www.youtube.com/watch?v=5eIQt9kbk7g The Legend of El Kabong


I took a look at some sail board photos and most were very rigid with some minor rippling in the sail material. Much like what you have there. 
Maybe enhance the ripple bumpmap? If that's how the model was textured.

Looking good though.
Later, Ron

[DocCharly65]

After turning shadows on............13.5 hours later. 

Okay! 13.5 hours BETTER! 
Really nice now!