Error: Unknown Filesystem

[Petro]

I'm clearly doing something very stupid here and just *not* seeing my 
mistake.

I've read through the documentation on www.gnu.org/software/grub/ and a 
few other places, and I'm just not seeing my mistake.

I am trying to create a "multiboot" usb installer like this gent here:
 http://www.panticz.de/MultiBootUSB

But I've found similar instructions in other places.

The one difference is that I can't use vfat/fat32 as I need, or at least 
want to use ISOs that are larger than that would allow.

I run parted, and create 2 partitions thusly:

address@hidden ~]# parted /dev/sdb
GNU Parted 3.0
Using /dev/sdb
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) print
Model: A-DATA USB Flash Drive (scsi)
Disk /dev/sdb: 16.2GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system  Name  Flags
 1      1049kB  200MB   199MB                boot  bios_grub
 2      200MB   16.2GB  16.0GB  ext3         data

Then I mkfs.vfat as such:
address@hidden ~]# mkfs.vfat -n "multiboottest" /dev/sdb1
mkfs.vfat 3.0.12 (29 Oct 2011)

Mount it:
address@hidden ~]# mount /dev/sdb1 /mnt/1/

Run grub install (I had to compile grub2 meself as I'm using Scientific 
Linux 6.3 in a VM and Fedora Core on the physical machine. Oh, wait. 
Fedora Core is at 1.99. Let's try those bits...
No difference.

Anyway:
address@hidden ~]# /opt/grub2/sbin/grub-install --no-floppy 
--root-directory=/mnt/1 /dev/sdb
Installation finished. No error reported.

address@hidden ~]# umount /dev/sdb1

address@hidden ~]# mount /dev/sdb1 /mnt/1/
mount: you must specify the filesystem type

Uh.... Huh.

So I stick the USB key in the lapdog and reboot.

GRUB loading.
Welcome to GRUB!

error: unknown filesystem.
Entering rescue mode...
grub rescue>

grub rescue> ls
(hd0) (hd0,gpt2) (hd0,gpt1) (hd1) hd1,gpt1) (hd1,gpt3) (hd1,gpt2) (hd1,gpt1)

grub rescue> set
prefix=(hd0,gpt1)/boot/grub2
root=hd0,gpt1

I get similar behavior if I use a ~250GIB WD USB drive.

What am I messing up?

Thanks,
Petro.
address@hidden address@hidden
:wq