So if you don't have or never need to install torsion style axles, this thread ain't for you.

So awhile back I posted here when my Featherlite trailer got t boned by a 50K CV, and the impact ripped off the axles. The lawyers are still fighting.

So I got the new ones installed, and getting them aligned was a major concern.
I figured axles being parallel was more important then crabbing within reason.
However, the replacement axles were brand new, matched, and custom built.
The design of the axles is basically a 10" lever arm, which means it has arc for travel, and the spindles are mounted in rubber.
So I measured off the outer axle square tube housing and bolted/welded them in place. After install, measuring from the axles I got them withing 1/32". I was satisfied, and moved on.

After get all the finishing other touches done, painting, wiring, wheels mounted, etc, I decided to throw a tape measure on the axle centers and see how everything measured up.
I measured nearly a 1/2" difference between the axle centers side to side.

So I decided, well lets road test this and decide how to fix.

After the road test, I was back under a 1/16" variance.

The lesson as I see it, with this style axle, measure off the housing, as I guess the arcs aren't necessary the same or in the same exact orientation when brand new ,and the rubber likely has never fully set since the axle has never seen a load, is my guess.