I'm a researcher, and need help from this community. I need to know if anyone remembers if the dart heads for the Whistlers and Dart Tags were completely hollow from stem to head from the years 2011 through 2017? If so, does anyone have pics showing the inside of one of these type of darts heads, perhaps cut in half? Plus with proof of the year the dart was manufactured or modified? Even homemade hollow dart heads would be acceptable. I know all of you are very experienced with this type of thing, so I'm pretty confident one or many of you will have the answers I seek. It will be greatly appreciated! Thanks for your time and effort.