Here's an excellent interview with the Grand Master of Downwind Paddling Mark Raaphorst
The only one thing I totally disagree with what Mark says is about the Hollow Boards yes they are a lot stronger but 100% styrofoam board goes way better in the ocean, I hate hollow boards.
Mark also talks about Prone Paddleboards I agree with what Mark says Prone Paddleboarding is fun I do both, it's great all round fitness to mix it up (using different muscles) plus it helps you read the ocean better, but Stand Up is way more fun.
Just look at the size of Marks brain you can see why he's a Genius.