Use /fetch url to upload (backup) file to remote https server

Hello,
I need help writing script which will create system backup and then upload file to remote https server.

/system/backup/save name=mybackup
/tool fetch http-method=put mode=https http-data=[/file get [/file find name=mybackup.backup] contents] url="https://myserver.domain.com/" http-header-field="Content-Type: application/octet-stream"

I also need to upload /export file=myconfig

However, it seems to me that issue is that variable limit to 4KB.
Can I somehow directly upload file? (Similar to src-path with FTPS ) ?
Thank you

http://forum.mikrotik.com/t/feature-request-tool-fetch-http-post-can-send-a-file/154710/3