If I had a way to measure the temps, I would do it.
There's already a gap of around a 1/4 inch between the coil pack and the timing cover to allow air to pass between the two but the insulating plate should also help reduce radiated heat. Hey, for $35 shipped, its a nice, simple and painless add-on.
You can get a smooth, quiet, floaty car and fall asleep waiting to get from point A to B, or enjoy getting there.
To be good at racing, you have to change your name to Sebastien.