Upgrade tasks for file from 3.6 to 4.x

Issue Summary

The file module for e-Commerce 3.x is now ec_file for 4.x - and I'm the new maintainer. One of the things holding me back from a beta release of this module is the lack of an upgrade path from 3.x to 4.x.

I need some feedback on whether these tasks, performed in the following order, will do the job:

1. private_upload should be installed and configured before any upgrade is possible, since it handles file download access permissions in 4.x.
2. Create a File download product feature for all CCK types which use file downloads.
3. Move all files from old folder structure to private_upload folder.
4. Register those files in the core file table.
5. For each file, add an entry to the (new) ec_file table.
6. Drop the old ec_product_file table.

Have I left out anything? I can't remember how file downloads were handled in 3.x - they did work using CCK types, right?