You're right, everything in salt that's good, takes time, and sometimes a little luck. I keep a piece of this either in my sump, or in the tank. For years now. I'm on the edge of dumping this big one, I have a small one in my sump to take it's place soon. I cut a 3" piece off in July. Then cut that piece in half, gave half to my cousin, and kept the other. It's a rotation, once it gets to about 10", it puts on size too fast. Not much demand for such large pieces, it gets too big for me too. I don't see many with these long polyps much. Here's the replacement, it's already "mushroomed", has a stalk, and is round, from about a month and a half in the sump. It's a 1.5" disk diameter, with 2" polyps.

It may take time to adjust to a system, but it's waaaaaaay easier than host anemone's to keep.