Honestly, IMHO I would use the 2"x11" U-bolts mounted across the springs (as shown on your upper bracket cap) instead of the other parallel U-bolts shown in the first picture. The first picture U-bolts don't appear to be completely vertical, nor do they appear to be kept from moving (possibly splaying out across the top axle bracket) as there are no positive retention grooves to help keep them in place like you have with the narrow U-bolts mounted parallel to the axle tubes.
The axle mounting in the first picture looks unsafe IMO, subject to either allowing the axle to shift on the springs side to side, or if tightened too much to try and keep them in place, may hinder axle rotation in the collars like they were designed for.
Others will probably chime in with their thoughts.
