I'll try to add to this soon. i'm going to take a selection of discs into work and weigh them, I know the Spondon ones are my lightest but not there actual weight, will also weigh EBC pro-lites and a few others.
This anorak fits well and its keeping me warm and dry in this weather.
As already pointed out, it's not the static weight alone that makes the difference. For instance, I have narrow track race Brembo discs in both 290 and 320 mm sizes. As it's the disc itself, not the carrier that accounts for the majority of the weight, a narrow track disc reduces the weight where it counts most. The discs themselves weigh about the same as what you've measured, but they can now carry a thicker disc which last longer and dissipates heat better. Remember, brake systems are a science and very difficult to understand, well, certainly for me.
They weigh virtually the same as the standard ones but are thicker at the same time. Were they the same thickness they would be lighter due to the narrower track using less steel.
Proper Ohlins race fork have two sets of mounting holes for the calipers.