I didn’t comment on a flip or plunge pool, only on the hardness of the rock. Your reply discussed a flip at the end of the spillway. This was puzzling since I hadn’t commented on that. So I scrolled back to see where the flip pool was discussed and found the article which proposed trying to jump over the crater in the spillway. This differed from a flip at the end of the spillway, hence my comment.
We were talking about two different things and talked right past each other.
Well hopefully you should have keys to answers, or good reference information, to your questions at this point. You have good observation skills and have put in good work in graphics and artwork in your posts - including good questions. This is always fruitful in discussions that I consider valuable with other FReepers such as yourself.