Multisite module shared configuration?

Hi, I'm developing a Multisite module that has some shared tables. I have settings that I've been using system_settings_form() for, but now I want to add more configuration options. The thing is, they should be shared as well. I don't want users to have to duplicate the settings over and over, so I'd like to store these configuration settings somewhere else.

What have others done for shared configuration? I'm leaning toward creating a mymodule_settings table, with the same layout as the variables table, and simply adding them there. Then I'll have to roll my own _settings_validate() and _settings_submit() function, of course.