Powermac G4 case won't shut after cpu upgrade

[Dorkenstein]

I bought a cpu upgrade for my g4 quicksilver and now the case, when shutting, catches partly when the optical drive (the really long one) and the heatsink on the cpu meet. The g4 case closes like a pair of scissors. My question is, if I replace the long optical drive with a newer shorter one, will the case close? The company where I bought the upgrade from will not answer my tech support questions although I have asked it several times. Thank you.