I am shooting Easton Axis 5 mm arrows. cut to 27 inches. They are 400 spine. I shoot a Mathews VXR. Pulling about 66 pounds with a 28 inch draw. I am planning on using Iron Will Wide broadheads, but do not know what size yest (100, 125, 150, etc). I also plan on using Iron Will's 25 grain Steel collar to reinforce the point. They have options of 25, 50, 75, and 100 grain steel inserts. I want to keep the arrows as I just bought them. I want to shoot "big boy arrows" with high FOC. I also don't want to compromise the structural integrity of the shaft. What do you think is the heaviest I can go with the inserts as well as the broadhead if I were to keep the 400 spine arrows?