Ah, sorry then if my previous message sounded somehow violent.
My idea is to install and run Plan 9 on a USB a few days, then copy the
disk image onto the HDD when I will be comfortable with it, so what I want
is to be able to boot from USB every time I plug it without relying on
external software such as GRUB and with hardcoded options.
But if I will take your suggestion if any other option fails =)