I think the difference is from what type of fletching we are using. I used Blazers and you used full sized fletching. This shows how using different fletching changes spine. Your arrows have more grains on the back which would increase spine. That's something people should pay attention to and why I created the thread asking people to give all of the info they have for their bow. I'd bet if we had a chronographed arrow from his bow the arrows would be stiff with the Blazers.