Can someone give directions on how to achieve a triple boot on 770?

I have mine already set up with dual boot thanks to fanoush' bootmenu and sebastian's easy instructions, choosing between ITOS2006 from internal flash, or ITOS2006 from ext2 partition on mmc. It's super-useful and works great!

Now, what if I want to add ITOS2007 hacker edition on the mmc?

Or, if it's too much mess, or requires getting rid of all the software installed in the mmc (no please!), is it possible (how?) to replace the internal ITOS2006 with ITOS2007 hacker edition, without affecting (if everything goes good) the ITOS2006 on mmc and the software installed on it?