I'm sure there are other people who can give you a better answer, but from my experience trying to bank fish below Sollie, I have a couple thoughts for you:
1) People definitely drift below Sollie at 5 ft or less, I caught my first salmon there on a day when the river was around 4.8', low tide, and it was stacked with drift boats
2) I might be wrong here, but from my experience there's not much to be had in the way of steelhead fishing in the tidewater below Sollie, maybe if the river is super low and cold, but generally I'd think they're just cruising through at a clip, unlike salmon who hold there