docker mysqlite cannot create database on mounted volume

Question

I am trying to install https://github.com/linuxserver/docker-plex on docker-toolbox on windows 7.

I am trying to set the config dir, which houses the sqlite library database to a larger external drive. I have succesfully mounted the drive into virtualbox and i can access it in docker-machine fine. However whenever I create the linked plex container and try to start it, I get the error that sqlite failed to create the database. Reading around I learnt that usually that is a permission error, how can I ensure the directory has the correct permissions?