I expect that you can do that, but is there really a need? There is a red pull tab in the trunk adjacent to the left trunk lid; pull on it and the mechanical system is disengaged allowing manual operation.
http://www.bmwz4roadster.net/brochur...s%20Manual.pdf
See pages 21 through 24. You may not need to do steps 6 and 7. Perhaps others here can chime in.