Spark: How do I Hide the list of users that have 'joined' a MUC Conference Room

Openfire 4.03

Spark 2.8.0

Our setup is not standard, in that we have a set of users (STAFF) that we DO NOT allow to chat to each other.  We are using the packet filter plugin to let the group MGMT talk to MGMT and to STAFF, while STAFF can only talk to MGT, not each other.

As an exception to this locked-down environment... we created one Conference Room in which we allow everyone to talk to everyone.

The packet filter does stop individuals from initiating separate chats with each other from the default Spark user interface, since the packet filter prevents any other user names from the STAFF group to show.

However, when in the conference room, a list of 'joined' users shows at the right of the conversation window - allowing users to initiate separate chats  by selecting the other persons name from that list of users.

Is there any way I can 'hide' this list of joined users in the MUC conference room?

Thanks,

Rich