use xbtool to make the bios 1024kb plus u can do stuff like colour the bios so u know when it's booting with the chip on and more
u can get xbtool
here
as for the dummy files find a 50mb+ file on your pc and copy it to the folder with the resized bios file and rename them 000dummy.000 and 0000dummy.000 that way it will push the bios file further from the middle of the disk making it easier for the xbox to read
*edit* it took me so long to type that u replied saying u fixed it already lol