The few times I hit bone (ribs mostly, shoulder once) my broad heads cut right through the bone. You hit high and get into the solid meat and the drag on the shaft will stop that arrow in a hurry. Same if you hit too far front. A lung shot is not what I would call "solid meat". Maybe you don't butcher your own deer and don't know any better. I find a lot of dead deer and arrow penetration seems to be a real problem lately. It has nothing to do with "Tuning", but is usually traced to extra light shafts and junky expensive heads. Who cares if the arrow passes through the deer anyway. If you cut both lungs or the heart or arteries the deer is dead. Don't give me one of those"I know a guy stories" about a double lung hit that got away. One lung maybe, two no. I like bowhunting, but for every deer drug out, one is hit and lost. People should stop blaming their equipment and spend more time studying what they are hunting and learning about their equipment.
If you use the same grain arrow out of a 40 pound bow and a 70# bow the 70# is going farther. I have a very short 70# longbow(I doubt I can still draw it) and the speed and distance it shoots is awesome.