You don't have to simulate it. The results are obvious. The case with "only front ground plane", and "two ground planes" will be same. If you simulate "only second ground plane" to subtract it's effect on your reflection you will get wrong results, because in two ground plane case, your second ground plane has absolutely no effect in reality.
I'm just giving you that example to show you that ground plane subtraction may not have any meaning except for certain cases where you want to see how it compares with a plain ground plane.
Can you give me one of those references which makes this subtraction?