The box just opened up looks like this.
After a quick inspection of the parts, I can comment that I am very impressed with the beam mounts' light weight and quality. The water jet cutting really works over areas that have two separated surfaces that make a very deep kerf. I think Ian Farrier made a huge effort to get the design right not only for the beams, but also for shipping.
Having the parts in hand, I can finally say that the instructions for adding the aft side bolt areas makes some sense.