The SE arms allow the axle to rotate around the axle center. There are two forces that stop the axle from flexing. There is the fore and aft movement that Nay is talking about, but also a twist/ rotate around the axle center. If you take three pencils and you glue them together like the two arms with the axle 90 degree to that. Now try to move the one arm down, and the other up. The rotational bind around the center is more than the fore and aft. Essentially the arms is trying to twist the axle like a candy cane. Just not going to happen. Only moves as much as the bushings allow.
That is why the tierod in the SW arm pictures moves up and down. The axle is essentially held in place for the rotational movement in just one place (the two bushings of the stock looking arm).
PS, Nay the comment re: price was not directed at you. Making those arms in small amounts in a machine shop is very time consuming and expensive.
That's a great explanation.
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