My BIBM install usually "just works" in perfect fashion, but I'm having trouble achieving something today and I wonder if it's not possible.
One of my many HDDs (HDD 3) is 4TB in size and so formatted as GPT. Currently, I use BIBM to boot from an Arch Linux install (Syslinux bootloader) on partition 1. In the BIBM boot edit screen, the entry just points to HDD3, and the "boot" field is blank. This works fine.
I've now installed Ubuntu into partition 2 on the same HDD. I want to add a new boot entry to BIBM, such that I can boot directly to that partition on the GPT drive, separately of the original Arch Linux install. But I can't work out how to do it. The boot menu won't let me specify a GPT partition to boot from; seems it's the whole disk or nothing.
Am I missing something?

Thanks!
Michael.