I've been running the river on a Glide SUP Mongo lately.
glidesup.com/boards/mong/ This board is like an epoxy..but with a bulletproof coating. i am rough on river boards and have been know to break a few. The Mongo is much tougher than I am. So far! I treat it like an inflatable, and not even a scratch.
It is a traditional surf board design so it probably wont get much use on class 4, but on class 2-3 it is great. Splats, squirts and it surfs EVERYTHING!
Next month I'll have it on the pacific coast of Mexico..stay tuned!
aaron