30d? You think thermostats start to open at 30 degrees below their operating temperature? So my 82 degree thermostat starts to open at 52 degrees? Rubbish. They do open earlier, but only a few degrees, and only very slightly. Having a bigger radiator will not affect this in the slightest, especially considering the water in the radiator will never be below ambient temperature regardless of air flow or road speed. The radiator is removed from the equation until the engine is at operating temperature. Find me one source that tells you differently and backs up your theory.
For the record, I'm originally from Germany so I go back to visit my grandparents quite often. They have never had to cover their radiator at any stage, and where they live (Kiefersfelden) it often gets well below negative 10. It would take some extreme cold for that to be necessary; maybe it gets that cold in Canada, I'm not sure. But it has certainly never been an issue for them in Germany. It would probably be more necessary on a diesel engine than a petrol engine.