Sorry, I may have lead you a little astray with my previous post.
What I was describing there was Customize Split.
I still think menus are going on disk 2, even in the regular split option, but as I type this post, I can't leave here to check, but you can.
Use the same source disk as you copied before. Go to Main Movie. It'll show you a break-down of the menus, main movie, and extras. Note the running time for the menus.
Now go to split. This will show a list of everything, with no description to tell you what each 'unit' is. Find the unit that has the same running time as the menus - this will probably be on disk 2 - the check marks will confirm that.
I've never tried altering anything in the regular split option, so I'm not sure if you can or not. You should be able to, though, in the Customize Split. (all this is if only if you don't like the menus on disk 2, and want to change it. If not, don't worry about it.)