If I upload a BIMx Hyper-model to Public Domain rather than Private Folder, can I ever delete it? Can I move it to the Private folder later on?
As for Private BIMx files. You don't need to use the BIMx Transfer site.
Save it to a folder, send that file to your client and they can open it with the BIMx docs app on their iPad. For me, when I tap on the file link in an email, it will ask if I want to open it with BIMx Docs. It does, and it saves it in your list of HYPER-MODELS. No need for BIMx Transfer site for sending private BIMx files.
Which means you don't need the SSA just to get your BIMx files to your clients privately.