First, find out what the problem is. The thermostat would not be related to you losing coolant. Does the car ever smoke at all?
I don't know about Fox's having this problem, but the 5N95 cars are notorious for getting a small pin hole in the coolant reservoir and leaking (which can be harder to spot than most people think).
On the thermostat, I think the stocker is supposed to be something like 190*. Most run like a 180* stat in the summer months. DO NOT get the 160*! It can actually cause your car to overheat!