Don't forget the trailing slash. Try to have at least three distinct sites as well. Place the most easily accessible first as they are traversed in order. All three are used. Common uses are things like security or reliability fixes.
Ports normally correspond to given versions of software.
If necessary, gently ask the original program author to make such distinctions clear. Even if all distfiles change, it is easier for the user to track cruft. Some ports don't always need to retrieve all files in all circumstances. For instance, some ports may have some compilation options, and associated files which are only required in such a case. Or they may need some files for some architectures only.