Hi
This is discussed here: Google Code Archive - Long-term storage for Google Code Project Hosting.. The trick will be to provide a "m2_null_element" as root object for the M2tk constructor.
Implement your "main" window as "direct graphics output" for U8glib. While displaying this "main" window, check for keys as described in the above link. Then set your meno via "setRoot" command.
Oliver