Both the deblet and mer installers will also include (I think fanoush's?) bootmenu installer which uses files inside the /etc/ directory to make the bootmenu.

Essentially the theory is going to be... Install Deblet or Mer, during that procedure it will help you setup a bootmenu for Deblet or Mer (respectively).. after that's done you can reboot the tablet and make sure you get a bootmenu for .. whichever. (and that it actually boots.. troubleshoot one OS at a time).

Then boot back into Maemo.. run the installer for Deblet or Mer (the one you DIDN'T install, obviously).. and when you get to the point where it asks to run the bootmenu installer say no..

Then go into.. I think it's /etc/bootmenu.d??... look at the 2 files that should already be in there (one for your flash, one for the first OS you installed).. copy one, and modify it for the new OS.. then there should be an icon in your apps menu somewhere for "Bootmenu Installer".. it'll go back through, read those /etc/bootmenu.d files, and recreate the bootmenu again.

This time when you reboot you should have 3 options....

In theory... this was LARGELY (ok, entirely?) based on memory...