A couple suggestions.......

1. Keep trying to figure out your current bow tune. It could be an arrow spine issue, rest tune, or a variety of other things that can also affect the on game performance of mechanical heads. (Knowledge is power)

2. Familiarize yourself with the different styles and their strengths and weaknesses, as well as which ones will compliment your set-up and it's performance and the game you are hunting. They aren't one size fits all and there will definitely be choices that are better than others.

3. When in doubt, err on the conservative side in cutting diameter and rearward opening blade styles.

4. Consider one of the many new short body, highly aerodynamic fixed blade heads on the market, such as the Slick Tricks, Shuttle T Locks, Rocky Mt. Turbo, NAP Nitron, etc.
I have found them to be highly forgiving and if they shoot as well as a comparable sized mechanical head then you gain no advantage by shooting a mech.

I personally only shoot mechanicals when they give me something a fixed head cannot, such as a very large cutting diameter to use out of a high energy bow. Never use them as a band-aid to not knowing why your fixed heads aren't flying true.