Joe, are you saying that even with minimal preload on the rears, due to you spacing the car up instead of winding up the springs, you're still experiencing bound helpers?

When the car is static, yes. I assume the helpers are working though because when I jack up the rear they do expand about half way, so I assume when I go over a bump they do their job and shove the tire back into the ground to keep that contact patch.

The only video i've found of the rear suspension in action is this. Looks like he has an aftermarket sway bar in the rear (I don't) and 7" springs (I don't) and 300lb rear springs (I don't) and a heavier NB miata (I don't)... So I don't know how comparable this is. He's also running .5" higher so probably a bunch of preload. But his helpers look fully bound to me and he seems to be pretty happy with it.

Essentially, I don't know what my suspension is really doing and I think only a good video with my application will tell me.

"I assume the helpers are working though because when I jack up the rear they do expand about half way"
Sounds all good to me then! I thought you meant they remained bound in droop, like the ones in the video.

I'm seriously leaning towards using FM-type spacers not just to jack my car up so the bloody low sump clears speedbumps, but to ensure I use minimal preload to get the helpers working as they should. Could be tested by just jacking up the car and seeing if the helpers extend. If they don't, use less preload and more spacers.

Thats my video which I did to verify the movement, no spring bind and that the helper stayed bound during operation. So basically in the video the helpers are acting as springs spacers and expensive ones at that...
At the time I was running 7" 350lbs springs, the extra bushing, and preloaded the helper about 1\3 down at full droop. Swaybar is oem MSM.
I have since gone back to 6" 350lbs springs, extra bushing, FM spacers and made my own spring centering setup that effectively extends the springs by about 1\3 of an inch. I am very happy now. I have good height, preloaded the helpers about half way down at full droop and the perches are no longer close to the axles like with the 7" springs.

Car feels perfect now. I will make another video to check movement when I get the chance.

My take on the spring centering issue. They center on the washer on the shaft and are made so they do not contact the shock body at full compression. (If the bump stop should fail...)

https://www.miataturbo.net/attachmen...ine=1338275211

And fully loaded before it went back into the car. I had to give it slightly more preload to get my desired ride height.

https://www.miataturbo.net/attachmen...ine=1338275211

The MSM was the heaviest NA/NB made and mine had well over 100# of added braces. With the perches run all the way up to the very top, I had to be careful getting out of the parking garage at work and often times used my frame rails as skid plates. My Xidas are now on the track car which is 95% stripped. It should be under 2,100 dry but I haven't weighed it. In that configuration, I'm still coil bound in the rear but just barely on similar ride heights. Being that low is fine (preferable) for the track car.

I don't know if there are any geometrical differences but everything that can be bolted on the rear of the chassis is from an MSM.