After >15' still nothing, just the green guy...
Oh, you aren't getting past the "green guy"? Well that is a problem with the kernel then if it doesn't even make it to the "android" flashing text.
That should have nothing to do with the sd-ext, that has to do with a borked installation (either a problem with ss7sys, or a problem with recovery flashing the boot.img), does the red led turn off at all or does it stay on?
It's possible to mount the ss7sys loop file to check out if the installation into it worked, just do this:
1. Start terminal session
2. cd /sdcard/multiboot
3. mkdir test
5. losetup -f (remember the output of this because you'll use it in step 6)
6. losetup [output of losetup -f in step 5, eg /dev/block/loop#] ss7sys
7. mount -t ext2 [output of losetup -f in step 5, eg /dev/block/loop#] test
8. ls test
If the file appears empty then there was a problem with the installation, if not there was a problem with flashing the boot image (which is likely).
One thing i noticed when i unpacked your ROM was that the boot.img had wierd permission settings, i don't know why but it's easy enough to fix.