@sarahlenker - sorry for the late reply… I missed this 
I haven’t tried adjusting the pivot-point - I doubt that will work as I need to change the origin (my understanding is that the pivot point defaults to the center of the bounding box but can be moved)
I want to update all my meshes. In that above diagram the origin of the model is at the bottom left of the red box. And, in this example, all the meshes (the cyan stuff) have a “z-offset” of 3,000. That offset is hard coded into the actual geometry of every object (i.e. my input geometry has points at x,y,3000+z etc. and not at x,y,z with a transform of (0,0,3000).
Right now, I apply a transform of (0,0,-3000) to the actor (that contains all the static meshes) and I can position things correctly. However, I still have a bounding box that is too big.
Am I making sense??