Wonko the Sane
How is it possible by you to answer any question any topic? How to become expert like you? Reading various forums topics would make we wise? or reading any programming?
What makes you expert?
I too want to answer questions posted in this forum. But most is not understood by me...
Sure, reading forums and docs, making a few experiments, being around for quite some time.
Unfortunately , especially for the last item above, there are no shortcuts, and the collateral damage in the process is that you get old (and possibly also grumpy ).
About the .iso, the idea is to extract/copy its contents in a folder, add to the folder (or in a subfolder, I am not at all expert in iPxe) your CONFIG.IPXE, then recreate the .iso using either genisoimage or mkisofs (most probably the original is made with genisoimage, but it won' t make any difference, as both are supported in the source script).
Do read the given links, they explain how to extract the boot files, it is very possible that ultraiso is "tricked" (just like it happened on the given thread):
by the "wrong length" of the isolinux boot file set by the "-boot-load-size 4", the given batch should work: