Well, after harvesting my three turkeys, I have come to a few conclusions-
Getting a proper dispatch shot into a turkeys head from behind is problematic and ineffective, at least for me. I failed in two attempts, neither of which resulted in fast deaths, while also managing to damage a wing on one which I had to remove. The other one did not fully bleed out to my satisfaction. So, failures, even though the meat was delicious after being smoked on a traegar.
For my final bird, I tried bleeding the bird upside down WITHOUT shooting it first. The bird was led over to the cross beam, made calm over several minutes, and then had both legs tied independently. The bird was lifted off the ground about 2 feet, and stayed calm the whole time. I play gentle music and talk to the bird, while I found exactly where the arteries/veins were in the neck. When I was satisfied I knew exactly where to cut, I used a large, freshly sharpened blade to make a deep, fast side to side cut while holding the birds head and holding open the wound. The bird did flap and struggle for about 5 seconds, and bled strongly for about 15-30 seconds. Tho it was more, well, personal, it also was a much cleaner/faster death and finished product.