When you have the uc_importer module enabled, there's a form in admin/store/products/import that you can go to that's specifically designed for Ãœbercart files. My importer is independent of importexportapi mostly because it threw a bunch of errors at me whenever I looked at it's pages. So I started from scratch and made a custom solution.

Edit: Actually, the URL might be different depending on your version. I can't remember when I changed it, but you might need to go to admin/store/import instead. It's a normal menu item, so you should see it in the menu links wherever it is.