How to make a custom keyboard layout be recognized as Latin so I can remove the US default layout?

I have a custom keyboard layout which MacOSX doesn't recognize as Latin, so it doesn't allow me to remove the US default layout.
I'd like to know what would make my layout be recognized as Latin.
Is the US default layout stored in a file somewhere? so I can compare it to mine and figure out what to change.
My layout is a modified US-international so it should be recognized as Latin with no problems.

Update: I solved it by setting the keyboard id to 1.

I solved this by setting the keyboard id to 1.

Disclaimer first: I haven't tried this myself.

In the message from user biovizier at 05-07-2007 10:44 PM in the MacWorld forum thread: http://hintsforums.macworld.com/archive/index.php/t-71629.html , it is claimed that it is possible if it matched both the ID and the name of an existing "approved" layout, and that the cache should be cleared to remove the old, compiled version of a such.

However, the thread is quite old so it may have been tightened even further in newer versions.