I don't think I have seen spoke tension mentioned yet in this thread. I were having repeated wobble issues, I would want to be sure it wasn't starting with slightly loose spokes.

Prior to reading this tread, I wasn't aware that "speed wobble" was a thing. I think I experienced it a few times as a teenager and intuitively shifted my weight and clamped the top tube in the right way. I don't think anyone ever told me to do that, but still, when I make a fast descent, I often clamp the top tube with my knees (before any wobbling starts).