"Preloading the Suspension"
I believe that your suspension on your bike should be preloaded similiar to what it will sit with your weight on it. This will effect all of your settings on attaching the hack frame.
Of course I'm a nube at this and could be wrong.........
I'm in the process of attaching a Dnepr hack to a 2005 R1200GS using a DMC subframe /mounts and I also questioned Jay on the way the upper mounts lacked clevises. He assured me that style of connection is more than adequate for the loads that it will see.
I'm looking forward to following the rest of your build!
(Too Many To List)