uploading to binary newsgroups

Why is it that every time I try to upload a large binary to a binary newsgroup I get errors.
For a 14 M file news.coax.nl reports No valid newsgroups in "alt.binaries.cd.image"
news.ams.chello.nl and news.text.chello.nl report Posting Failed (Article Too Big) reports.

Also, when I try to download files from there, they are often incomplete. All the other news servers have the complete files but chello.

Is there anyway to get a proper news service with chello?

I think there isn't, i'm not shure but I think you can only upload 5 MB