Shoshone at 6-8K cfs and up is formidable. It is a very clean but narrow line, easily identifiable via a very convenient scout. River covers the bike path at higher flows, and that's where the most trouble happens. There is a reason the commercials are shut down, so take your a-game.
And I seem to remember a huge wave that appears in the 'horseshoe bend' below Grizzly around 10-12K that can flip unwary boaters in a stretch that is normally considered class II water.
So have fun, but watch yourself!