Cardboard thermal throttling avoidance

Hi,

Just wanted to ask about steps to take to minimize the potential for thermal throttling with Google Cardboard. These questions are probably more generalist then specifically to cardboard itself but I wondered what would be the best measures to take to reduce gpu load? I know there's some generalist advice here: http://docs.unity3d.com/Manual/OptimizingGraphicsPerformance.html

But there's a couple of areas with Cardboard specific areas which I'm wondering about optimising one of the following and how much of a saving I'd get (in an arbitrary sense)

1. If I use a smaller Render Texture for the end image, i.e. for half the screen size?

2. I have an outline effect that's currently being done with a second pass on geometry. I wondered whether to use edge detection instead but can't use Unity's build in image effect correctly. Is there a way round this?

3. A way of limiting gpu/cpu clock speed by an amount to avoid the issues in the first place?

4. An alternative to using Pow() in my shader to get whether a object's world normal is in the same direction as my "light source". Note that I'm not actually using lighting in engine, I'm actually setting a point or direction for a light to emit from which "lights" objects based on whether their world normal is facing the light source.

Thanks,