Thanks for the info!
And yes, it's the "dogbots" I'm using. I discovered them thanks to you, Inso, and have been on my top spot for not-cylon minis since then. Predatorpt's suggestion of using robogear helmets as cylon heads was spot on, too.
And now, a mere three years later after buying some, I have finally taken the finger out of my arse and have glued and primed a prototype.
That said... There's a change of plans regarding the use of necron torsos.

I'm going to make two style of cylons. The older models (5-series), and newer ones (6-series).
For the 5-series I'll use the CMG battlesuits, because they look chunky and functional, with no regard to aesthetics (as the original slave robots would have been designed).
It's for the newer 6-series that I'm going to try to achieve a sleeker design (as would be when robots start to design themselves). For the legs, I think the ones from the Tau XV-25 stealth suits will look like a nice evolution: they are completely armoured, but share the same three segments anatomy. Then, necron torsos (likely destroyer ones, with the "rib" gaps filled and back "spines" filed), and converted heads. Not sure yet what I can use for the arms...