The formatting software known to be compatible is Apple HD SC Setup and Drive7. Many others do work but engineering does not have a list of compatible formatters.
At Ease will provide immediate feedback on whether a specific drive is compatible or not. If At Ease detects an incompatible hard disk, the Lock Startup Volume checkbox is dimmed. You will need to contact the publisher of the driver software to see if a compatible version is available.
Here is some information from the At Ease 2.0.3 Read Me:
Locking the startup disk
==================
When you choose this option, At Ease locks your startup disk by installing security software on it. This security software cannot be installed on hard disks that have been initialized by driver software that is not compatible with At Ease 2.0.3 for Workgroups.
If At Ease detects an incompatible hard disk, the Lock Startup Volume checkbox is dimmed. Contact the publisher of the driver software to see if a compatible version is available. The At Ease security software cannot be installed on any hard disk partitioned with A/UX.
Updating disk drivers
================
If you need to update the driver software for a locked disk, first choose Security from the Options menu in the Setup program and click the Lock Startup Volume checkbox to remove the X.
Changing the startup disk
=====================
If you lock the startup volume, do not change the startup disk selected in the Startup Disk control panel. If you change the startup disk, your At Ease startup volume will not appear on the desktop when you restart the computer, and you will not be able to reselect it from within the Startup Disk control panel.