x-sendfile performance

We need modifications to an operating site made in Drupal 5 with MODIFIED core.

Files are served via private files transfer due to access protection, but this is putting a heavy load on the server due to the amount of media material on the site. The site is slow and we have been looking at several solutions.. Making a X-send file module is our idea for a solution.

Everything needs to be tested carefully on a premade testsite, as the main is live and access must not be interruptet..

The solution should also be produced quickly..