raidframe - a configf question

[yancm%SDF.ORG@localhost]

I am preparing a replacement system for my 10 year old home
firewall/nat/webserver.

The new system is i386 (amd 2600, 2.25 G RAM, 3x 120 GB HD), running
NetBSD_6_Stable w/Generic kernel.

I had 3 disks, so *loosely* followed Ch. 16 (raidframe setup) of The Guide.
Initially I installed 6.1.4 release onto wd0, upgraded it to 6_Stable,
configured raid on wd1/wd2 using the example config from the guide:
START array
1 2 0

START disks
/dev/wd1a
/dev/wd2a

START layout
128 1 1 1

START queue
fifo 100

Now to my question....
I've already reconfigured wd0 as a raid disk, installed bootblocks with -t
raid and verified I can use it in the array manually.
But I think I'd like to add wd0 into raid0 as a hot spare.
I can do this interactively, but it is not persistent.
Is this as easy as updating the config file to:

START array
1 2 1

START disks
/dev/wd1a
/dev/wd2a

START spare
/dev/wd0a

START layout
128 1 1 1

START queue
fifo 100

(raidctl -c config_file raid0)

1) It was not clear from my reading of the man page or guide, if I could
reconfigure a raid array without destroying it.

2) If what I propose is OK, what other steps might I need or want to take?

thanks,
gene