@brian For the record: I updated my initial V6 offline installation with the latest, also via offline update and all went as expected.
One little “papercut” type issue: could you “blink” and/or shade the install button when it’s clicked? The installer seems to take quite a while to do anything visible, so the user isn’t sure he/she successfully clicked the button, and this user at least doesn’t want to keep clicking to be sure, not knowing what that could bring.