Disable RSS feed

Hi there -

I have two subdirectory blogs that are no longer active but that I want to keep available to search engines for seo reasons. Both blogs share a theme with other blogs in my wpmu setup and I'd like that to continue if possible so that I don't have to remember to update multiple themes if I make a change to one.

Here's what I want to do: Disable the RSS feeds or keep them from pinging when I update posts on the inactive blogs (updates = fix a typo, etc). I'm looking for a solution that will:

- Not require me to change the theme's functions.php code, since the inactive blogs share a theme with active blogs (I know I can disable feeds by adding certain code to functions.php).

- Not require me to assign different versions of the same theme to active/inactive blogs (I know I can replicate the theme and call it something different, but am trying to minimize maintenance as described above).

- Not require me to use the cbnet ping optimizer plugin. I tried it but found two problems: It stopped working after I upgraded to 3.1 and it used a huge amount of database resources to ru (I know there are other plugins out there that might do this, but I've found none that have been actively maintained in the last year or so).

Does anyone know of a work-around that meets my admittedly unique set of criteria? Thanks!