You double up on the original file by merging it with itself with copy/b bios4.bin+bios4.bin=bios4x2.bin
Then after you create bios4x2.bin you will repeat the above syntax which would be
copy/b bios4x2.bin+bios4x2.bin=bios4x4.bin
bios4x4.bin is the file you burn to a 4002 or 4096
BB