Install Solaris 8 bootblk from cdrom while still booted

I have been experimenting for some time with Veritas Volume Manager and root disk encapsulation on our aging Solaris 8 systems.
Since I am using a copy of a disk from a hefty SunFire 4800 on a smaller V240 I am encountering some strange issues. Perhaps I will bolg about all the tricks soon.
Heres one.
I want to reinstall a bootblock on a newly mirrored rootdisk.
However since I am running a disk built on the wrong architecture some device paths are not normal or broken.

One odd result is that veritas vxbootsetup is refusing to install the boot block.
Since I have had to do this several times it is very slow booting from cdrom i wanted to install it without rebooting first.

Issue:
After mirroring the boot drive you want to make the new disk bootable.

# /etc/vx/bin/vxbootsetup -g rootdg -n

/usr/lib/fs/ufs/bootblk: File not found
eeprom(1M) not implemented on SUNW,Sun-Fire-V240
/usr/lib/fs/ufs/bootblk: File not found
eeprom(1M) not implemented on SUNW,Sun-Fire-V240

Solution:
Dont rerun vxbootsetup or it will try to create even more partitions on the new disk.

No need to reboot from CD ROM
Normally you would boot from cdrom to do this like this.

ok} boot cdrom -sw
...

# /usr/sbin/installboot /usr/platform/`uname -i`/lib/fs/ufs/bootblk /dev/rdsk/c1t3d0s0

Instead put the cdrom in the drive without rebooting and install it as follows (all on one line)

# /usr/sbin/installboot /cdrom/sol_8_204_sparc/s0/Solaris_8/Tools/Boot/usr/platform/SUNW,Sun-Fire-V240/lib/fs/ufs/bootblk /dev/rdsk/c1t3d0s0

I hope I just save you an extra CD reboot.
But you better test the disk to be sure it boots I have encountered some strange booting issues.