Download methods

Hi.
I tried 3 methods for downloadable products, so this is the result:

1) Force download: Gives an error, because I put large files (up to 1Gb)
2) X-Sendfile: Doesn’t work on my server
3) Redirect only: It works, but everyone can download the files with original link

So, is there a way to protect DOWNLOADABLES folder and allow download just only after payment?

http://wordpress.org/extend/plugins/woocommerce/