I have been trying to get MEPIS 11 GRUB to chainload the antiX GRUB installed in the root of sda6. The chainloader +1 command kept returning an error message. I found a GRUB legacy manual at:
========= SCRAPER REMOVED AN EMBEDDED LINK HERE ===========
url was:"https://wiki.archlinux.org/index.php/GRUB_Legacy"
linktext was:"https://wiki.archlinux.org/index.php/GRUB_Legacy"
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that had the solution. When the following is used the antiX GRUB chainloads OK:

title Other Linux
root (hd0,x)
configfile /boot/grub/menu.lst

In my case the (hd0,x) is (hd0,5).