I have one friend who has shot 2 does with tekans with good results. He told my other friend about it and he, Matt, decided to shoot it. Keep in mind that Matt shoots jak hammers and has had great results......he is a mechanical fan...well, that is, if it is a jak...
On a recent hunt in the midwest, he had a 25 yard broadside shot on a 140 class deer. He centered the lungs. Upon picking up his arrow, he was horrified to see both blades gone! The blood trail was weak, then decent, then gone. So was the deer.
With mechanicals, it is very important to be careful. There are a few heads out there that stand above the rest. Stick with them. Jak Hammers, Vortex, Steelheads, Spitfires...and for the bigger ones, shoot enough horsepower.