One of my biggest sources of combat science are professional athletes who compete in full-contact combat sports. They are a great source, no argument there.
I also had a friend who has never competed in professional martial arts, but lays his credibility on the fact that he's been in 600 fights thoughout his life, was a pro powerlifter with a 720-pound raw squat, was a collegiate wrestler, and STILL pushes himself to learn new things considering how he signed up for Judo lessons a few months ago.
He SWORE by dim mak and went so far as saying that if one is trained in dim mak, he or she wouldn't need to learn any other martial art. Even coming from him, it is hard to believe. But on top of his combat experience, he was a very educated man with a Master's degree. Granted, his degree was Psychology, so he may have been using his psychological skills to convince me some ********, but I don't think that was the case. He is a good guy with a cool family life on top of a noble job.
I'll look into dim mak and see what I can find...