I don't know what all the information flying around is about, but all you need is one separate, universal /boot partition to hold the kernel images and related files. This should've been created with the first distro installation. GRUB must be re-edited and re-installed to MBR after the final distro is set up.

How to manage the different systems falls entirely on the primary menu.lst and the hdx,y with the sda lines. The hdx,y will be same for all of the entries; it specifies where to look for the image and this is the /boot created earlier. If it was sda1, then it'd be hd0,0. If it was sdb6, then hd1,5. So on so forth. The sda/hda lines will be different for every entry because it refers to the root partition.

Since you already are booting well, but you just want to re-order the list, look at which of the menu.lst resembles the menu and edit it. After that, install it to the MBR.