This is another video from the same boater but 2.5 miles upstream. These are well prepared boaters with a good boatman leading, and they had two incidents in the first five miles. Look at how tight his rig is too. No extra crap sticking up anywhere, solid boater, good assistant in the bow. The river is moving here.
From when he eddied out to Murph's Hole ( where the boatman ejected) is exactly one mile. In the vid going slow he does it in just over six minutes. So true river speed if you don't try to go slow is likely 12 to 13 mph, with minimal eddies.
Also I want to point out the three craft on river right at the end of this video were pulled over because of this incident below. Brad and his trip came two days early as the pass was very late to open with all the spring snow. My crew opened it up on June 14th so we could launch on the 15th. They launched the next day. He helped us shovel for a while in shorts and flip flops. Sure seemed like a nice guy.
The river really is only class IV, but with access and evacuation very challenging one must be very organized and prepared.
Not trying to talk you out of this at all, but I have seen the aftermath when things don't go well.