This is more of an archival post for myself since part of the documentation for [cached]isostick (a USB stick that can emulate optical drives) is down and the project does not seem maintained any more.
Since isostick only supports FAT32 filesystems, ISOs larger than 4 GB need to be split up into multiple parts.
Here's the explanation for how to do this from the now offline isostick forum:
The isostick can only read files from FAT32 partitions. Unfortunately, FAT32 has a maximum file size of 4GB. To overcome this, isostick can read ISO files which are split into multiple …