My version of axle support plan B

One thing though, an axle that is de-cambered is bent. If the steel hadn't reached its yield point it would have returned to its original shape once the stress was removed (elastic deformation). Once the yield stress in exceeded it will no longer return to its previous shape (plastic deformation). It will take on a permanent strain/bend.  It will also become work hardened and more brittle.The next time it is over loaded it will take more stress to bend it further.  The good thing here is that we're taking about pretty small deflection angles because the tube is so stiff so its not like these things are getting bent into pretzels. 

Here is an interesting video discussing this and showing one way to straighten/recamber an axle. 

I could maybe see trying to do this at home with a high capacity jack if a safe way could be found to cradle the axle and chains. 

If a shop isn't available that will do it, the same basic idea should work for the torsion axle but you would need probably a 1/4 inch thick or better short piece of 3 inch steel angle to protect the torsion axle tube from getting pushed in by the bottle jack. If the axle is still crowned you could place the jack at the frame attach point on the side that shows negative camber. If its flat in the middle then place it in the middle. Not for the faint of heart, but better than just cranking down on the 1/2 inch bolt I think. Take your time, release and measure, and please be careful. 

Take another look at the first video. The axle is tied down by the chains on both sides, which go from the axle, over the jack, and back to the axle on either side. So the jack just tensions the chains and pushes on the axle. Nothing should move or come off the ground. The angles the chains make with the axle need to be kept to about 45 degrees or so as the first video shows. Shallow angles will just result in the chains sliding along the axle. So, you'll end up bending a couple foot sections of the axle a little at a time.  The jack will probably need to be at least 10 tons capacity. 

I think its actually pretty safe if you leave the wheels on, which you'd want to do anyway so you can see the camber angle.  If the jack slips out of the chains it will just fall down. Chains aren't like wire rope or cables, they don't really stretch much so they're not going to fly around if the tension is released. Even so, if you try this, stay off to the side of the chains while operating the jack, and take it slow.