I'm not sure if you can unassign the shift key or not, but you can always assign it to a button you'll never use (ie. a keycode that's not mapped to a button on your control panel). Then you can manuaaly map all your menu buttons to any spare keys you've got left over. Know what I mean?
If you want to talk to a real expert then ask the guy who created it, AndyWarne. He's a member here so you can look him up and PM him directly.