This is the age old knock on Corbin. Nice stuff, generally well made, but have a problem and customer service stinks. My bags look gorgeous, but I must confess I have not held them up to the bike in the sunlight.
That being said, I have no real beef over this with Corbin. I frankly don't blame them for refusing to discuss altering a bracket. Any issues with breakage or a crack and they will bear the brunt of a claim when the bracket they designed was not used, or at least in the way they designed it.