I used Spitfires years ago for one season. Hit one of the biggest bucks of my hunting career square in the shoulder and the arrow went in about two inches. I was about 3 inches to the left of where I wanted my arrow to go. As soon as I saw the lack of penetration of that arrow I got a sick feeling in my stomach. Never found him. My fault, poor shooting. I'm pretty confident the Muzzys I was using before the switch, and changed back to after that season, would have did the job. I've had a couple similar hits with Muzzys and did not lose any of them. We got that deer in rifle season, scored close to 160 (field scoring, never officially scored).
I did shoot a buck a few days latter with the Spitfire , and the head did well going through both sides of the rib cage.
Good job on the buck, glad you were able to score!