I did get the D-Box settings for helicopter use working well enough. I cranked up the motion settings into the 50's and I adjusted the roll a bit lower than pitch because the actuators are not in a perfect square and that seemed to make things feel uniform. I was able to leverage self-centering like this and it wasn't throwing me off. I dropped from the max of 60 until the thunks stopped.
Keep in mind that helicopters tend not to do much in the way of barrel rolls or vertical climbs, and you need to feel the more subtle angles which the stock settings are not even close to providing.
It's not as compelling as the NLRv3 was for helicopter use for cyclic feel, but it's acceptable now and it brings other effects to the table. You can feel a take off and landing much better and some other feelings in the air.
The new G-Belt support for DCS helps sell motion without as much range, so that's working well and helping make up for the lack of motion.
For flight use the Engine RPM HAPTICS SUCK ROYAL DUNG! Being able to feel the engine at all in flight destroys the motion and you loose any smoothness. When you ease into a bank and can feel the engine haptics it makes the motion feel horribly notchy and like the D-Box has no resolution. When you turn the Engine RPM off or way down so you can't feel it, motion feels smooth again.
I had noticed the engine hapics destroyed motion with planes earlier and "thought" it was OK for helicopters. That was because I hadn't dialed things in to feel the cyclic motion at all. Now that I have some of the cyclic feel I was looking for, the rpm effect ruins motion just like for the planes.
So haptics for flight are a complete waste. Unfortunately I don't have Simshakers for Aviators set up which I've mentioned repeatedly. I plan to do that ASAP now that I have the rest feeling pretty good and I'd like to feel some tactile too.
All that said, I feel like I now have motion feeling good enough all around that I'm "overall" happy with the D-Box. It could definitely use more travel for flight, and probably feels better in Rally with more travel, but it nails track use, does a pretty compelling rally, and handles flight "acceptably".