Not sure what FTP server the newer v2.x version single bay/single drive My Clouds but for the older v4.x My Cloud one may be able to edit, via SSH, the /etc/vsftpd.conf file to change the settings of the FTP server. See the following post for a bit more information that may give some ideas or pointers if using a newer v2.x My Cloud.
https://community.wd.com/t/mycloud-ftp-users-home-dirs/139922/2
Of course if the /etc/vsftpd.conf file gets overwritten upon each restart of a v2.x My Cloud then it presents another issue to workaround.
