Question about installing boot manager in sysinstall

[Mark Ovens]

I've got two SCSI drives, da0 and da1. FreeBSD 6.3-STABLE is installed 
on da0 and da1 currently has Mandriva Linux on it. The boot manager 
being used is Grub.

I now want to replace Linux with FreeBSD 7 but I'm expecting that I may 
end up with an unbootable system because da0 (6.3) will still have Grub 
but da1 (7) will have the FreeBSD boot manager. Since Grub uses files in 
/boot on the Linux partition it won't work as these will have been wiped 
out.

So, I...

Run sysinstall
On the partition editor screen, select da1, delete the Linux slice, 
create a new FreeBSD slice, then 'Q'
At the bootmanager screen, select the FreeBSD boot manager
In the disklabel editor, create the partitions in the slice

OK, that's the new disk configured and I'm now back at the Select Disk 
screen.  Do I now select da0 (the existing 6.3) and in the Partition 
Editor just hit 'Q' without changing anything, then select the FreeBSD 
boot manager, and finally, in the disk label editor just hit 'Q' again 
without changing anything - especially the NewFS flag!!

Will this install the FreeBSD boot manager on da0 but not touch the 
existing partition/slice set up - i.e. it won't trash my 6.3 system?

I've read the Handbook but the example it gives for 2 disks assumes that 
you are creating FreeBSD partitions/slices on *both* disks, it doesn't 
have an example for just adding an existing disk to the boot manager.

What makes me nervous about doing this is that the boot manager is 
installed in the MBR where the partition table lives.

The other option I may be able to use is to run boot0cfg(8) on da0 (6.3 
system) *before* installing 7 - or maybe run it on both disks and don't 
select a boot manager during the install.

So, what's the best (i.e. safest) way to proceed?

Oh, and before anyone says, yes, I *have* backed up all my data ;-)

Regards,

Mark