bsdlabel problem for gmirror

[Andy Firman]

I am following this guide exactly on 5.3-stable:
http://people.freebsd.org/~rse/mirror/
and I am using 2 fresh Western Digital WD800JBRTL 80GB drives.
The first time I did the gmirror "Approach 1: Whole Disk" it 
worked having one drive on ad0 and the other on ad2.

Quick first question:
Having each drive on a different controller is preferable right?
The howto has the drives on ad0 and ad1 which would be same controller.

The first time was practice.  I have just failed to do it again
5 times in a row and I am really, really frustrated.
I am most likely making a big mistake at this point:
bsdlabel -e /dev/mirror/gm0s1    # create custom partitions

So my second question is when you start "a" partition at
offset 16, partitions "a" and "b" overlap.  So how would you 
recommend making them NOT overlap?

--------------------------------------
This is what the bsdlabel is/was for ad0s1:

bash-2.05b# bsdlabel ad0s1
# /dev/ad0s1:
8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  a: 10485760        0    4.2BSD     2048 16384 28552
  b:  4194304 10485760      swap
  c: 156296322        0    unused        0     0         # "raw" part, don't edit
  d: 20971520 14680064    4.2BSD     2048 16384 28552
  e: 120644738 35651584    4.2BSD     2048 16384 28552
-----------------------------------------

THIS IS REAL ONE for gm0s1 that I made and saved with no complaints:

# /dev/mirror/gm0s1:
8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  a: 10485744        16   4.2BSD     2048 16384 28552
  b:  4194304 10485760      swap
  c: 156296322        0    unused        0     0         # "raw" part, don't edit
  d: 20971520 14680064    4.2BSD     2048 16384 28552
  e: 120644738 35651584    4.2BSD     2048 16384 28552
---------------------------------------------


Thanks for any help.
-Andy