I currently have 11.10 and 12.04 Beta running side-by-side. Since installing the beta, I am presented with a GRUB2 menu every time I boot up, which selects 12.04 by default. (Aside: when the 11.10 kernel updated from 3.0.0-16 to 3.0.0-17 this option did not appear in the GRUB2 menu.)

When I open Grub Customizer in 11.10, it shows 11.10 kernel 3.0.0-17 as the default, when I open Grub Customizer in 12.04, it shows 12.04 as the default.

How can I change GRUB2 to pick the latest 11.10 kernel as the default? (Latest means that if 3.0.0-18 is released it will become the default, and so on.) And also stop displaying the menu (I only boot into the beta when I have something specific to test).

Generic answers that apply to any two Ubuntus running side-by-side are preferred.