You're missing the QR. Only one side should be bolted to the boss, the other should clamp with a niffty little QR 'bit' (that's a technical term that is!).
CRC has a lot of spares, I think I'm going to have a similar problem. IIRC BITD this was a problem with maguras and seem to remember the introduction of the QR mounting. I've never ran them so don't know too much, Neilll does seem to be the man.