Thanks for taking the time to take and post these images.
This is the most complete series of images of this rapid I have seen. Tells the entire Frog Rock story very well.
Over the years, I have run this rapid a lot in a kayak and several times in a raft. If a person always runs hard river left the danger of the rapid might well be under rated, as on the left it is a easy move and typical of a lot of drops on the upper Ark. Never took the time to check it out in detail on river right as due to all the concerns about going river left I really concentrate hard on looking at the go left slot. (I believe 100 percent that you go where you look!)
From the photos, I can see that some one who did not know about the danger "could" head river right and not realize the bad choice till it was too late.
Thanks again for the images.