I have killed a boatload of animals with Thunderhead 125's. I shot these heads way back because I was "sharpening challenged" and always felt that a really sharp chisel head broadhead was better than a not sharp cut on contact head that I had tried to sharpen. I now shoot German kinetic Silverflame XL's, which I have finally learned how to get really sharp, and know from experience that the penetration is better with the two blades than with the Thunderheads, That being said, you put just about any really sharp broadhead in the right place and it will work just fine.
Bisch