Hi John,
I'm going to guess and say that Frolin probably drove in, so he was on the other (south) side of the river to begin with. I like his camera position, because he can climb the opposite hillside and get some elevation. He has a better view of the train. Unfortunately, unless we bring a rubber raft, I don't see us getting there by hiking down from the train.
From a timing standpoint, the best Cascade shot is a morning shot from either the east abutment or from down below on the east side. The best afternoon shot would probably be between 1PM and 2PM on the west side or broadside from below. It would be "high-sunnish", but if you wait until after about 3PM, the sun angle is just right down the throat on the west side. No light on the side of the train. I have half a dozen Cascade shots from the west side. The only one that was decently lit was from Pete Lerro's first trip in 2011, and that was taken right after lunch.
/Kevin Madore