How do I change the default group for newly created domains?

How do I change the default group for the files and folders within httpdocs for newly created domains?

To give you some context; I want my staff to be able to SFTP into my server using THEIR username and password but able to read and write in all of the domain's located in var/www/vhosts. The problem is that Virtualmin sets the group to the same name as the owner. And so I can't just add my staff to a single group like apache so they can read and write in all the files and folders with a group writeable of apache.

Thanks!