I never found a good method. My basic process was as follows.
1) Collapse all objects.
2) Select all between the original PC objects and 8thy's (Click on the first, Shift click on the last).
3) Cut and paste.
4) Scan all objects for any commands that reference other object numbers, and increase them by 1 if it's not a PC object. Off the top of my head, Call Object Function, Hide Object, and drawing status by index need to be changed. Drawing Status by index needs to be increased by 2.
I found it to be a rather tedious process, which is why I gone slowly on this particular part.