>
 >>
>> PATCH with media-type application/tus-v2 may be a better solution 
>> as you can define the body any way that you like, which may include a 
>> custom (header) section in the body containing metadata such as the 
>> information you can not currently describe in Content-Range.
 >>
>
>
> Content-Range requires the range to include the end offset which is not 
> always available. We need something like “Content-Range: 42-/*” ...
> 
Suggest multipart/vnd.tus, pending registration of multipart/tus after receiving feedback, as a PATCH media type. Multipart explicitly allows "42-/*" as a boundary, however you want to define it within your media type. No custom headers needed. If, of course, you insist on not just using FTP or WebDAV. ;)
-Eric