As much as I hate to say it, I think this may be a user error. I have both a Tubus rack and a Jandd and have not had a problem attaching either and my BG is spaced at 135mm. I looked at your bike on Cannondales site and (nice bike, BTW) it uses standard LX hubs so I would assume your rear dropout spacing is either 130mm or 135mm. Either rack will flex to fit that. Maybe your rack was squashed a bit in shipping.