Dear ruymbeke,
I follow your steps and now I can boot my 1G usb2 ext. usb stick.

Thanks a lot

Best Regards,
Mike Kranidis.

P.S. what is the filesystem of the loop file minirt_usb2 ??? I tried to mount (after decompretion) using mount -o loop ./minirt_usb2 /mnt/test but it was unsuccessfully can you guess why??