How can I easilly combine i386 and amd64 installs on one cd/dvd/usb-stick?

[tahina]

I'd like to install both i386 and amd64 variants of ubuntu onto a usb stick. Does anyone know of any pre-made such images?

Or, come to think of it, this probably requires grub and partitions on the usb stick...

Any knowledge of nice scripts or something to ease this kind of setup for ubuntu?