That is one of the examples I was trying to make a point about. When you read Dr. Ashby's reports it is important to understand what he is saying. The issues come about when you try to apply the data incorrectly.
One cannot assume because a combonation works well on one animal it will be the best for all. I also don't recall reading anything about time to incapacitation. Another point that needs made can given by the following example: This type of work was done for handgun ammunition. The goal was to determine what worked best/quickest more times than not. The group selected 500 animals based on size, weight, and bone structure/content to best match humans. At the end of the study there were clear winners when the caliber and ammo was used correctly under the right conditions. Law enforcement conditions were not "the right conditions" and the data had to be masaged to find the "right" answer for that application.
Issues? You bet ya!
First people didn't understand what was being said and thought because there was a clear winner under the right conditions the "winner" was best used for all applications and failures became apparent quickly.
Second folks who had Docterate degrees in Math and statistics jumped in and said 500 animals wasn't enough data points to draw conclusions from. Medical doctors concluded to many other factors also applied in real world shootings, such as mental condition, drug use, barriers, shot angle, etc. I won't bore you with all the other details and 15 years worth of data from both sides of the what worked best coin. Today there is a clear winners and indrustry trend have been set and are working very well. I also forgot to mention the fact that all 500 animals where shot in a calm state unaware of what was happening while they were connected to equipment that monitored brain activity, blood pressure, heart rate, etc.
I saod all of that to bring home this point. Dr. Ashby is breaking new ground but is only touching one very limmited area of the subject at hand. In no way can this data be used as reported on all maner of creature if one expects valid results under all conditions, for all sizes, shapes, and make up of game. All we can conclude at this point is if a combination penetrated beter in his reports most of the time it will on lesser animals. That does not mean it will kill quicker, but it probably means it is more likely to kill the animal at some time by reaching vitals.
As to the bow weight doesn't matter. I'm sure that is also true under certian conditions because today modern 50 lb bows on one model can shoot as fast as some 70 lb bows of another model. Again we must consider all factor and the speed of the bow is one one of many.
Another example to note ot Terry's Buffalo shot in Montana (I think). When one arrow fail to penetrate he used a back up arrow of a different type and it worked successfully. He could conclude the second arrow should always be used because it worked better than the first. When I review the data I see about 20 possible items that could have been different from the first shot to the last and conclude I learned almost nothing. The next go around the results could be totally different.
I just want to ask everyone to understand if anything is changed in the form of arrow size, weight, speed, type of bow, animal shot, angle of the shot, and on and on...don't be surprised if your results are different. If Dr. Ashby at some point created a list of 50 broadhead and ranked them from best to worse you would still need to take 5 from the top, middle, and low end and try them for your application(s). You would then be able to draw conclusions by reviewing your results and his and if you and I are smart enough figure out why the results are differnt and fine tune our choice. (in simple terms).