Configure PMBR to Find Loader on GPT Disk

[Jason C. Wells]

After setting up a GPT disk and installing the boot blocks with:

    # gpart bootcode -b /boot/pmbr -p /boot/gptboot -i 1 ad4

The system wants to boot:

    0:ad(0p2)/boot/kernel/kernel

I manually intervene to cause the system to boot:

    1:ad(5p8)/boot/loader

How do I configure the boot blocks to do this without human intervention 
on a GPT system?  boot0cfg doesn't seem to be the correct tool for this job.

Thanks,
Jason