Grub2 on Mac Mini with USB Drive?

[Ken Mandelberg]

I run Linux off an external USB hard drive on a Mac Mini. Until now I 
have been using Legacy Grub with Ubuntu. The only way I have been able 
to make this work is to have refit boot off a Legacy Grub CD which gets 
a kernel off a partition on the internal drive, but sets root on the USB 
drive.

Ubuntu 9.10 offers Grub2 and I'm wondering if I can do something with 
less pieces. I particularly don't like maintaining a shadow boot 
partition on the internal disk, or depending on the CD to boot.

I tried just letting Ubuntu 9.10 install with Grub2 on the USB drive. 
When I boot with refit off the "legacy" partition, I get a screen with 
"Using Load Option USB", then a dozen lines of not found errors, and 
finally a line that says that external hard drives are not well 
supported by Apple firmware.

Is there something else I should try with Grub2, thats an improvement of 
the awkward setup I use with Legacy Grub?