I used them for years until a friend had me try Wac'ems. I got tired of having to re-sight for T-heads when changing from field tips. And yes my bow is tuned properly.
I had my bow tuned up. Shot my field tips. Put on a wacem, shot right with the field tips. Took the same arrow, took off the wac'em, put on the T-head and it was consistently low left or left. They seem to plane or something.
they are a good head for sure, but I just found something better, for me.