I just figured out a way to do them — with great deliberation and attention, but it’s happening. And with a good distal knuckle on my middle finger, which is a shock. Keeping my elbow up and sitting in the right orientation is a huge part of it.
I suspect this will be a big part of my practice routine now since I’m so pleased to be doing them. They still feel strange and alien, but that will improve with time.
Update: I’ve also noticed that I can’t do it without the back of (especially) my index finger pressing against the string below the string it’s on. The middle finger just barely misses this; I figure that this is just part of the nature of doing that, and if that becomes a problem in a given piece, then I’ll deal with it individually.
It’s surprising how nice this makes me feel. I had sort of felt like a half-assed harpist without the ability to do that, and I’m not sure why. I think that that tendency of my middle finger knuckle to collapse really bothered me a lot, and although it still does it a lot, at least it doesn’t prevent me from rolling a nice, juicy four-fingered chord.
I can also play the entire 4-note chords I put into “Zdes’ Khorosho“, which is really nice because it really does add a decent amount of juice to that part of the arrangement.