I didn't have a problem with stones in the NWT or the Yukon but I did have a substantial problem with bugs (monster flies) clogging the rad in the NWT. I ended up stopping at a Ford dealer (I believe in Hay River) and I bought a stainless steel bug screen (made by Cloud Rider
Link). It works well and it would also protect against rock hits. It doesn't restrict the airflow much, I use it in the southern US in 90+ temps while hauling without problems