There is one issue I have found, the CB User ID is not retained or at least there is no option to retain the CB User ID during export and import.
After my successful import and export, my kunena forum threads were pointing to different users as result.
You are trying to use the package for use that it was not intended to fulfill. If you are doing a migration of a site, it is much better to move tables with migration tools that link packages and associated tables. That is mysql work. If you are not sure how to do that, try to find a firm to support you. (p.s. I don't= cbjuice is a hobby).
CBJuice does not modify the userid because there is no guarantee that it will be the same if you are moving users between sites via an add. I can consider a user-beware option to userthe userid on an ADD only. It could lead to significant corruption. Put this kind of comment in the help forum and we will see what other users suggest.