Much time later...
I discovered the easiest way.
- Use Winrar, 7zip to extract EFI capable ISO to Directory.
(Like a windows 7/8/10 disk)
(or a Linux Disk)
[NOT a MAC Disk]
- Use a partition manager to toggle boot flag
But if a disk contains large files over 4096 megs, they wont work in fat32
For Mac Disks, Best to convert the disk to DMG, then use
A. Win32diskimager in windows (Its basically dd)
And just select the DMG (drop box "all files" first)
and click "write"
It will add the EFI partition, and the HFS+ parition to the USB, and it will boot.
This has worked for all the disks I needed.
YUMI now has a UEFI beta version that works well for USBs at least. – LJD200 – 2016-10-28T08:11:47.047
2YUMI has an EFI boot mode? – TardisGuy – 2013-12-03T02:54:50.450
1I don't believe it is EFI/uEFI compatible as it stands. If you are looking to boot ISO files, this can for at least Windows 7 installers although I think it just uses the files from the CD to launch the installer. I use it on my primary USB key to reformat Windows XP and 7 PCs, as well as several ISOs and live CDs for diag. – Mat Carlson – 2013-12-03T17:13:13.973