curtain rail and a problem ceiling

[Pauline Moon]

There is a step in the ceiling in a bay window in my flat and I need advice on how to put up a curtain rail. There is only one thickness of plasterboard at the highest bit and there are two thicknesses at the lower bit.

I was thinking of using 'no nails' to attach pieces of wood to the ceiling at the two higher corners, so that I would then have 4 points that are all at the same height, where I could attach the brackets (or whatever they are called) that hold up the curtain rail - would this work? (I don't want to pull down the ceiling!)

Pauline