Not so much an electrical question as a practical one -- we are trying to replace a standard 9cm plastic ceiling rose with a metal one incorporating a hook in order to suspend a glass light on chains. We were originally sold an 11cm one on the grounds that "as long as it's bigger than the one it's replacing, it will be fine", but the distance between the screw holes is too narrow to allow it to be attached over the existing back plate. We subsequently bought a second hook, which is the same diameter as the plastic rose, and has screw holes in the same position. However, it is completely flat across its base, whereas clearly the wiring on the backplate is slightly proud of the wall, so it is hard to see how we are going to achieve a secure fit by simply screwing it in over the top. Any suggestions (preferably not involving more expenditure!!)?