I have those same tires in the stock 205/40R17 size on stock 17x7 size aftermarket wheels and I have been very happy with the size and with the tires. They have good quick turn in and agile handling, which is my goal for tires. The 215s are also a pound heavier, and it's always good to save as much unsprung weight as possible.
The Ford engineers who designed the car put a lot of thought into every aspect of it including the tires, so I found no reason to deviate from the stock size tires.
Here is a video with one of the engineers who worked on the car discussing the suspension, in the video he says-
The tire is very well matched to the geometry and the torque of the engine.
View: https://www.youtube.com/watch?v=M7YKS9CnpJg