The more pins you add the more power gets thrown to the rear, on a loose track you want to go as light as you can get away with to keep the rear squared up. I think Cam uses 5 pins on his indoor high grip setup! i use 4 pins on my local track which is similar to yours, try it and see what your laptimes say. Every situation is different i can only go by what i see!

From what I have heard is that AE CST ratings are lightly off from everyone elses, either way just drop down from where you are, its all relative!