Be aware that there is still a problem with disklabel.  If you do
disklabel -r -e, It seems to write the boot record *from* a NetBSd
partition to MBR!  I haven't had time to track this down but I am
reasonably sure this is what happens.  Not using -r seems to avoid
the problem.  I found this when trying to change partition type
from unused to MS-DOS.