There is a very simple way to create a fully persistent USB of eOS. You will simply require the following:-
-Oracle VM VirtualBox (free)
-Copy of the eOS .ISO
-A 32gb+ Pendrive (I use a SanDisk 32GB)
All you need to do it configure a new virtual machine with a virtual HDD greater than 9gb. In settings, be sure to enable USB support also. Set that up, and set the boot image to be the eOS ISO file you already have. Boot up the VM to the installation screen. With your USB attached, follow the instructions until you get to the screen suggesting YOU WILL DESTROY ALL DATA ETC ETC and select the bottom option. It's along the lines of "do something else". The next screen allows you to assign partitions. You should see your USB listed as a drive (Linux detects SanDisk thumbdrives at actual drives) and you can go ahead and partition it up. I recommend and 8gb root, a 4gb swap and the rest assigned to home. If you're not sure how to do this, check out the method detailed here. The partition set up is the same.
That's it essentially. Restart, boot from legacy mode using the USB and you're done. I'm not sure if UEFI can be incorporated here, but I just disable it to use Linux anyway.