HFS+ are Linux compliant:
"The Linux kernel includes the hfsplus module[12] for mounting HFS+ filesystems read-write."
Wikipedia
So just wondering if they should work with HDMU or any of the E2 images.
I think hfsplusprogs is a plugin that allows you format disks in HFS+ (but I'm not 100% sure about that), which should suggest it is an accepted format.
I'm a Mac man so ext formatted disks are useless for me.
Thanks