whmcs_user

Hi, I've checked the options for Product Downloads Distribution (see: https://docs.whmcs.com/Product_Downloads_Distribution ), which is working fine for smaller files but not for really large ones. The (technical) problem is that the dl.php does not seem to support chunked file retrieval and distribution for download - while I can upload a really large file (5, 10, 25 or even more GB) thru ftp, the dl script by whmcs is trying to load all of the file into memory and then send it to the browser. Not good for large files. An setting the php memory_limit is of no real help here. There could also be the problem of sessions goind stale, as downloading will take some time. So I thought of using an external download provider script (that one works well for downloading large files in a chunked way, splitting the content into 206 partial content fractions) and hooking it with whmcs to provide file access restricted to a client that bought the product. But looking a the list of available hooks and esp. the api does not seem to have the downloads attached to a product logic implemented - or am I missing sth.? Any good idea how to achieve the distribution of really large files through whmcs?