gpart, slice starts at 0

Hi,

I did this to get a disk partitioned:

#!/bin/tcsh
###############################################################################
#
# File name:	FormatSamsung160GB
#
# Description:	This script formats a thumb drive connected as da0
#
###############################################################################
#
gpart destroy -F da0
diskinfo da0
dd if=/dev/zero of=/dev/da0 bs=512 count=34
dd if=/dev/zero of=/dev/da0 bs=512 count=34 seek=312581774
gpart show  -p da0
gpart create -s MBR da0
gpart add -t freebsd da0
gpart show  -p da0
gpart show  -p da0s1
gpart set -a active -i 1 da0
#
# The following line always gives an error:
#
# gpart create -s BSD da0s1
gpart bootcode -b /boot/mbr da0
gpart bootcode -b /boot/boot da0s1
gpart show  -p da0
gpart show  -p da0s1
gpart add -t freebsd-ufs -s 512MB -l Samsung160GBroot da0s1

The script results in this output:

FormatSamsung160GB
da0 destroyed
da0     512     160041885696    312581808       0       0       19457
255     63 34+0 records in
34+0 records out
17408 bytes transferred in 0.012732 secs (1367260 bytes/sec)
34+0 records in
34+0 records out
17408 bytes transferred in 0.023717 secs (733983 bytes/sec)
gpart: No such geom: da0.
da0 created
da0s1 added
=>       63  312581745    da0  MBR  (149G)
         63  312581745  da0s1  freebsd  (149G)

=>        0  312581745  da0s1  BSD  (149G)
          0  312581745         - free -  (149G)

active set on da0s1
bootcode written to da0
bootcode written to da0s1
=>       63  312581745    da0  MBR  (149G)
         63  312581745  da0s1  freebsd  [active]  (149G)

=>        0  312581745  da0s1  BSD  (149G)
          0  312581745         - free -  (149G)

gpart: Invalid argument
[X220]...Appl/Some Tools (root) > gpart show da0
=>       63  312581745  da0  MBR  (149G)
         63  312581745    1  freebsd  [active]  (149G)

[X220]...Appl/Some Tools (root) > gpart show da0s1
=>        0  312581745  da0s1  BSD  (149G)
          0  312581745         - free -  (149G)

I have now two problems which I do not understand. First, why do I need
this line and why does it fail?

gpart create -s BSD da0s1

Second, why does this slice start at 0?

=>        0  312581745  da0s1  BSD  (149G)
          0  312581745         - free -  (149G)

I use this as an starting point:

http://www.wonkity.com/~wblock/docs/html/disksetup.html

It worked for me some time ago.

Did I miss something very, very simple?

Erich