setting www & non www for mapped domain

hi, got domain mapping working.... normally these htaccess codes define whether www is used or not in the standalone....

www
RewriteEngine On
RewriteCond %{HTTP_HOST} !^www.
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]

non www
RewriteEngine On
RewriteCond %{HTTP_HOST} !^my-domain.com$ [NC]
RewriteRule ^(.*)$ http://my-domain.com/$1 [R=301,L]

but how is it done with domain mapping enabled? both r working, but i dont want to enable both to halve the google juice..

strange... coz i thought only the non www was available in a multisite installation... guess not... nice surprise too..

thnx.