aria2c fails to download to a path that is mounted to FTP

Question

I would like to setup a downloader on a raspberry PI to download into my NAS (MyBookLive), since I don't have enough space on the PI. I don't want to install the downloader into the MyBookLive since it is running out of CPU and MEM already.

1. I've mounted the NAS through FTP to the PI with the instructions that can be found if you follow the link. Basically I did:

curlftpfs -o allow_other ftp-user:[email protected] /mnt/entresol/Public

I am able to copy files back and forth /mnt/entresol/Public:

cp README.md /mnt/antresol/Public/temp/

2. I've installed aria2 and I am able to download a file to a PI dir:

aria2c -d ~/aria2c/ ~/aria2c.log https://github.com/ziahamza/webui-aria2/blob/master/README.md

But when I try download to an FTP mounted dir:

aria2c -d /mnt/antresol/Public/ ~/aria2c.log https://github.com/ziahamza/webui-aria2/blob/master/README.md

I receive following error:

12/12 22:32:46 [ERROR] CUID#6 - Download aborted. URI=https://github.com/ziahamza/webui-aria2/blob/master/README.md
Exception: [AbstractCommand.cc:350] errorCode=16 URI=https://github.com/ziahamza/webui-aria2/blob/master/README.md
  -> [AbstractDiskWriter.cc:222] errNum=95 errorCode=16 Failed to open the file /mnt/antresol/Public/temp/README.md, cause: Operation not supported

Any ideas?