I too read the comments about oil thermostat controls not working well on the street. However, my Improved Racing thermostat works AWESOME! It begins to open at 180* and fully opens at 200*. On the street with mild driving it hangs out right around 190* on the gauge all day long. Their thermostats really work. Also, other than the first start of the day, the oil warms up quickly. I can drive to an atuocross and let the car sit for 2 hours and it will only take about 5 minute for the oil to warm up to be over 150* and usually the time I'm up to the start line it is 180*+
If you are running an air to oil cooler than I assume you are running a quality plate and fin cooler such as Setrab. For sizing your oil cooler, here is a good reference:
http://www.setrabusa.com/products/oi...ine/index.html
The above cooler sizing references on Setrab's site will show oil cooler sizes *much* larger than I've seen recommended on this site. If all you are doing are street driving and autocross you can get away with a smaller cooler. If you are going to run full track days then I'd size it according to their specs.