Here are a couple of pictures from underneath the trailer - one from the front and two from the rear. All of the pieces are 1"x#" box tubing, 3/16" wall thickness. I welded a piece along each frame rail, then two pieces across the trailer - one basically where the torsion axle
went across, and one to the rear of that, even with one of the smaller cross members. The axle
flanges were then attached to the channels running along the frame rails, with some shim pieces to make sure the wheels track correctly.