It is possible to boot the following linux ISOs with persistence from your E2B USB drive:
linuxmint, XiaOpan, ubuntu, YLMF, Puppy, Slax, Ubuntu, LUbuntu, Fedora, Backtrack 5, BitDefender Rescue (old versions only), geebox, kali linux, kaspersky, PCLinuxOS, Porteus, StartOS and XBMCbuntu.
They can all be on the same E2B drive and all boot using different persistence files. The E2B drive justs needs the one partition for E2B (partition #3 and partition #4 which should both be unused/free).
You can even have multiple persistence files used by the same one ISO. For example, you could have a Bob_Ubuntu.mnu for Bob and a Mary_Ubuntu.mnu for Mary - both would boot from the same Ubuntu ISO but use different persistent files.
You normally will need to copy and edit a small .mnu file and make an ext2 file using RMPrepUSB for each ISO.
For more details, please see here.