resizing the root file system

Are there any precautions I need to take after resizing the root fs?
I don't see /etc/rc.d/resize_root taking any.

I moved the other partitions away, booted single user, enlarged the 
partition, fsck'd / and did resize_ffs. I did another fsck / after that, 
which showed no errors, but (as expected) more free blocks than before. 
I then went multi-user but suddenly the additional free space is gone 
and fsck complains that the primary superblock and the backups are 
inconsistent. Indeed, dumpfs -as shows the primary sb reflects the old 
and the backups reflect the new size.

This is all on -6 in case it matters. Please don't tell me I need to 
update, that's the reason I need to enlarge /.

I tested all this on a (dd'd) copy of the root partition at the end of 
the disc, which went well. I could try going single user again and dd 
that copy back to the front.


Another question is why I needed to /boot/ into single user. I /went/ 
single user but couldn't mount -u -r / from there (ENOTSUP).