Aws.yml layout and security of accesskey and secret key?

I have a aws.yml fill in a similar fashion to database.yml. There are
staging, production areas, which include instance_url, keypair_name, see
below. Im not storing this in svn, but copying across the file with cap
on the after_setup callback.

So the reason for the topic; I wanted to get some feedback on the
security of this approach. Also, what is everyone else doing in the way
of layout for their aws.yml files.

cheers
adam

#-----------------------

aws global settings

#-----------------------
aws: &aws
access_key: ------
secret_access_key: --------
account: --------

#-----------------------

environment settings

#-----------------------
staging:
keypair_name: staging------keypair
id_rsa: “~/.ec2/id_rsa-staging-------keypair”
instance_url: not-yet-defined
s3:
download_bucket: -----
static_bucket: ----
artwork_bucket: ------
<<: *aws

production:
keypair_name: ------keypair
id_rsa: “~/.ec2/id_rsa------”
instance_url: domU-------------
s3:
download_bucket: -----
static_bucket: ----
artwork_bucket: ------
<<: *aws