How to boot from a slice other than "a"?

[Philip Hallstrom]

Hi all -

I've got a remote server and for one reason or another have it setup like 
this:

Filesystem     Size    Used   Avail Capacity  Mounted on
/dev/da0s1a    248M    180M     48M    79%    /
/dev/da0s1h     14G    496M     13G     4%    /mnt

/dev/da0s1h has an exact copy of /dev/da0s1a using dump/restore.

I want to configure things so that the next time I reboot it will 
automatically boot from /dev/da0s1h without me having to do anything 
(since it's remote I can't interrupt the boot process).

I know I need to modify fstab on da0s1h.  And if I was on the console I'd 
interrupt the boot process and type in 0:da(0,h)/boot/loader, but I'm not.

And I'm not entirely sure what files to tweak to make that happen.  I've 
read the boot/loader manpages, but am just not getting it today.

Anyone know what files to tweak?

-philip