the server can impose any limit it wants ... it doesn't have to tell you what that limit is, or why. If you have problems sending big files, but not small files from yourscript -- then try sending the same files with a different script in a different language, or with a browser.

If stting $DYNAMIC_FILE_UPLOAD to a true value didn't help, then i'm not sure what to tell you ... the docs seem pretty clear to me ... setting it to tru means that the Request objects won't try to load whole files into memory, they'll only read them on demand when POSTing them

My guess is that hte remote site has a limit on the fle sizes it accepts.