That will be fine. I'm using that setup myself now, because I didn't want to lose my GT.
Angerwound: disk.bin is not a file, and my feeling as to why you didn't get rebanned quickly in those cases is due to ONLY changing the hdd key and creating a new gamertag. This could, of course, be wrong.
Disk.bin is formed of data stored on the hdd, effectively the partition table, or part of it. Possibly the boot sector (though I doubt that myself). It is created when you use the backup function in EvoX. If you open it with a hex editor, you will find two mentions of xbox.com with regards to passports. One account is your xbox, the other is your GT. It's covered in better detail in other threads.. Such as the What we know (fact) thread.. (Or whatever it's called).
Anyways.