You need to put them above line 52 - not just above the Ubuntu entry. Not below. Otherwise it will be modified, just as the file itself says.
### BEGIN AUTOMAGIC KERNELS LIST
## lines between the AUTOMAGIC KERNELS LIST markers will be modified
## by the debian update-grub script except for the default options below
You need to put them above line 52 - not just above the Ubuntu entry. Not below. Otherwise it will be modified, just as the file itself says.
### BEGIN AUTOMAGIC KERNELS LIST
## lines between the AUTOMAGIC KERNELS LIST markers will be modified
## by the debian update-grub script except for the default options below