The thing I'm a little confused about is where the flex/rotation comes from. Does the spring eye rotate around the bushing, or does the bushing stay fixed with the spring and the shackle rotate around that?
When you torque it down like crazy, it squeezes the bushing, so it's harder for it to rotate against the shackle. The rubber seems to have no ability to rotate inside the spring, except for the actual twist of the rubber. With the greasable bushings though, maybe they can - although the grease channels are against the bolt/sleeve if I remember correctly.
If the bushing width with two of them together is the same as the sleeve or slightly shorter, then I suppose you could pretty much torque away and the bushing could rotate around the sleeve. Thing is, especially on the hangar side, the hangar sides are not parallel to the bushings, they are narrower at the bottom, so torquing the hangar way down will squish the bushing on the bottom regardless...
Enough rambling. /forums/images/graemlins/whistling.gif