I am touching back on this thread because I just realized nobody actually answered one of my main questions. To wit,
how exactly do I upload them? [books in public domain in US but not Canada] I understand that MR has a US server available, but how do I access that?
For the other newbs, I found by trial, that you need to upload the book as normal, and then use the "Report Post" button, and provide an explanation in the the dialog that you need this attachment transferred to the U.S. server.
Simple to do, but difficult to find the guidance.
Hope this helps some other bewildered soul.