Rewrite from www to not www version

Is everything okay with my version

[jetteroheller]

After the big drop in Google index from 27th June, I resarch every possibilty for problems.

I use since 1996 the same content provider.
He has always each domain made reachable under

example.com
www.example.com

Now I noticed that some of my domains had been indexed as

subdomain.example.com
www.subdomain.example.com

Since this could, like in the Google search news forum discussed, be a problem, I use now the following:

#<AID>
# FollowSymLinks is needed for mod_rewrite, without you'll get
# 100% 403 errors
Options +FollowSymLinks
RewriteEngine On
RewriteBase /

RewriteCond %{HTTP_HOST} ^www.sub.example.com
RewriteRule ^(.*) [sub.example.com...] [R=301,L]
#</AID>

Is this best way to solve this maybe problem?