Today I tested making and adding other multiboot USB Flash drive images to my E2B USB Hard Disk.
I have now made new images of different USB Flash pens that were made using the following programs, and added them to my E2B drive:
PenDriveLinux Universal USB Installer
XBOOT (make using Syslinux and use the 'Replace menu.lst' option when asked)
WinSetupFromUSB (use the 'Combine menu.lst' option when asked)
LiveUSBCreator (with persistence)
These images all seem to work OK using the latest 0.016 MPI version though I haven't tested them all thoroughly but at least one payload seems to boot on each one! So if you already have a working USB Flash drive made using one of these utilities, try adding them to E2B.