I have had exceptional results with stingers! It's definately not the broadheads. If you can't get them to fly, it's likely you won't be able to achieve satisfactory results with any other BH. Even with canted blades, or less than perfect alignment, I've been able to achieve consistent and accurate flight with these heads. Even out of my compound at much higher speeds.
I shoot my super shrew long bow (51@28) with GT 35/55 (.500 spine) @ 29 3/8" with 300g up front at 27.5" draw length. I can shoot any broadhead in that weight range that I've tried. You are probably too stiff, causing inconsistancie and/or shelf/ riser contact. May also be a brace height issue.Good luck.