How can I prevent iframes from being stripped out on save for non super admins?

I'm in the process of converting about 20 blogs on separate installations to a WP multisite installation. We have a couple blogs set up for testing and we're running into problems with posting YouTube videos. For non super admins, when we include just the link in the editor, it doesn't always work and when it does, it doesn't mesh well with the design. I installed the Ultimate TinyMCE plugin which does what I need it to when I'm logged in as the super admin but iFrames are stripped out for all other users when I save. I've tried a few things already (deactivating and reactivating plugins, modifying kses.php, giving editors admin privileges) but nothing works. Would you guys have any suggestions?