Hidden Master Menu… Is this the only way?

Well, I have a network where I want all sites to have a common menu… I want that menu WAY at the top of each page of every site. The theme’s primary location is below a graphic in the masthead, and I want that to be for the sites to mess with (they see that menu as their only one to make their own, and NOT the master one..)

I do NOT want the site admins even seeing anything that will allow them to mess with the master menu, but they can add their own local menus all day long…

I’m thinking of a brute force php include way up in the header, and hard coding the ~150 menu items, thus allowing all sites to share the same menu, theme-independent, and most importantly NOT showing up as a menu in Appearance they can alter.

Multisite Shared Menu seems to be able to be edited by site admins… How can I accomplish this without hard coding in header.php or similar?

thank you