Many people, including myself, have used Spitfires with great success. Excellent mechanical. I typically don't aim for bone but I did have a Spitfire slice a rib clean in two. Of course, maybe I'm just not aiming for the right bone. If you are looking for a great mechanical, the Spitfires have a great track record. And they don't have a rubber band or you don't have to attach them to your cable or they don't have to perform some trick to close and open. They just kill deer. I would recommend not going to mechanicals just because you can't get a fixed head to fly with your field tips. Try some other fixed blades to see if more tuning is needed. Nitrons and Montec G5's have shown to fly with field tips if your bow is tuned. They both have 1-1/16" cutting diameter. Get into larger cutting diameters and 4 blades and, in my experience, you may find fixed not flying as consistant. I have had Muzzy 3 blades fly true but I'd get drifters with the 4 blade. Thunderhead 3 blades have flown well also. The main thing is get your bow tuned whatever blade you are using. Then you can use whatever blade you like.