By chance I discovered something about the Vulcan hard drive that I never knew about and don’t see in the manual.
On booting the Vulcan by accident I happened to press the space bar and a menu from the Vulcan firmware opened. It gave me a choice of which slot to boot from or which Vulcan partition to boot off of. I wish I'd known about this years ago.
Sadly it’s only on the IIgs and not the IIe. I’m using the Vulcan Gold firmware. Don’t know if it’s on the earlier versions