problem with boot0cfg on a twe?

very -current

# boot0cfg -B -d 1 -s 1 -v twed0
boot0cfg: write_mbr: /dev/twed0: No such file or directory

# boot0cfg -B -d 1 -s 1 -v twe0 
boot0cfg: read /dev/twe0: Operation not supported by device

# ls -l /dev/twed0
crw-r-----  1 root  operator    0,  76 Jun  8 23:32 /dev/twed0

# df
Filesystem    1024-blocks      Used     Avail Capacity  Mounted on
/dev/twed0s1a      253678     67506    165878    29%    /
devfs                   1         1         0   100%    /dev
/dev/twed0s1d      126702      7682    108884     7%    /var
/dev/twed0s1e      126702       192    116374     0%    /var/spool
/dev/twed0s1f    28341292   2393116  23680874     9%    /usr
/dev/twed0s1g     4058062        54   3733364     0%    /usr/home
/dev/twed0s1h       63256       858     57338     1%    /root
/dev/twed1s1e   961291472 536501578 347886578    61%    /data
procfs                  4         4         0   100%    /proc
/dev/md0           126702        14    116552     0%    /tmp

and the current man page for boot0cfg implies that i can install
  boot0    - crt only
  boot0sio - sio only

i have many systems with /boot.config having -P that seem to be
willing to go either way.  what am i not understanding?

randy