This is indeed no possible currently.
The problem is that we want to avoid beginners being confused with those two possibilities. Plus, they would likely not put the correct link to the file which wouldn't be in the secure folder and that wouldn't work... We would have to display a listing of all the files in the safe folder with navigation in order to be able to select the file. That would be better. It's in the todo list.
In the mean time, what you should do is increase your PHP upload limit. For example, you could follow this page:
phpdevteam.com/blog/2010/01/increase-the-file-upload-size/
Then, you would be able to upload files over 10MB.