Jacking under a std leaf spring axle tube next to the U bolt will not bend or crush the tubes....their too thick.
I've jacked fully loaded enclosed/stock and flatbed trailers with 1750 lb on up to 10000lb axles under the tubes when on the side of the road changing a flat tire.
My old truckers special 12ton hyd shorty jack (10"X10" base) look like the red jack in the picture.
It came with short legged channel that fits over the top of the jack to cradle the axle tube. I've had it repacked 3 times in all these years.
What ever method you use make a dry run at home especially those drive on ramps. On the side of the road 25 miles west of slapout ok isn't the place to discover it didn't work.