Shortly after I bought my 2004 Rockwood I dedcided to upgrade the tires to a higher load rating. I called Rockwood tech line and asked them where I should jack from. They said to put the jack under the axle. Just in case, I called AL-KO, who made my torsion axles. AL-KO said absolutely not to jacking under the axle, frame jacking only. So much for Rockwood giving the correct information about jacking under the axle.
I place a floor jack under the frame between the tires with an 18" long 2"x4"x 1/8" thick steel steel rectangular tube on top of the jack pad, which distributes the force over an 18" long section of frame. These frames seem easily damaged, so I don't take any chances.
Steve