I made two of these, of 3/16" steel...debating whether to double up the leaf, to 3/8", or to add another set of clamps further in towards the axle tube.... UPDATE 8/23/13, decided that single thickness was strong enough (minimum tensile strength 58000 psi), so I installed the other retainer strap on the other side, cut the excess off the bolts, cleaned the threads and torqued the nylocks to 75 ft-lbs