Try fixed heads. I can only assume that with a good broadside shot, at that distance, there is no reason for the arrow to not pass through. I can only assume you got crap penetration. I have seen it many times with others using mechanicals. Back in my compound days, I used mechanicals to see what the buzz was about. I was not impressed. I got crap penetraion on many occasions. I tried spitfires, as well as many others. I tested them on hogs. People would send me the latest mechanical for me to test, I would go out hunt hogs and send them the results. I just dont see the reason behind mechanicals when fixed heads have been tried and tested through out time. Why fix what is not broken.
I know many outfitters who will not let hunters use mechanicals. I wont let people use mechanicals on my land either. I get sick of having wonded deer go off and die without being recovered.