Nevermind, I think I found it thanks top this site :
http://www.wiseontech.com/hack/wordpress-hacking-multiple-blogs-on-one-set-of-tables-2
Down in the comments they refer to more modern installs. I did this:
Edit the wp-db.php file in the wp-includes directory.
In the function set_prefix($prefix) section
After :
foreach ( $this->tables as $table )
$this->$table = $this->prefix . $table;
Added :
$this->options = ‘wp_’ . ‘options’;
Or whatever your new prefix is. Testing now, I’ll write again if I experience any issues. This is a case of spending 4 hours a few nights ago, and going around in circles. Then after only 20 minutes of trying tonight, getting it working. The benefits of rest apparently.
