Sdl4 - this is the first time I've heard of one leg being disconnected. They all three should hold the center plug in place. If those tweeters were mine, I would repair them with aluminum filled epoxy. You might consult Rob before doing anything and see what he thinks.
That fore-structure performs multiple functions. It protects the fragile dome. It also spreads the on-axis energy for broader dispersion at the high end. It also acts something like a phase plug in that it retards the leading energy at the apex of the dome to average it with the circumferential energy closer to the surround. The hex shape of the center plate is engineered as superior to a round one.
Considerable effort went into developing that structure, so I find it interesting when various pundits recommend removing it. I suggest trusting Jim's work, those kinds of details represent the meticulous care he took in the design process.
What I am looking at is the sharp edges on the back side of the structure, both the 3 arms and the plug. We didn't address that level of detail in the 80s, but I wish we had, and I now am attending to unfinished business. I do not yet have confirming measurements (working on it), but I (believe that I) can hear improvement via contouring the edges of all members and coating with soft agents. Work in process.
