Just a bit of information about the Karankawa. We're not extinct, yet. I believe that my family from my father's side are direct descendants of the Karankawas. My family came from the Matagorda area and almost all of my Uncles were well over 6 ft. My oldest Uncle was 6ft. 6in.
My belief is that when the Spanish missions took in the Karankawas and converted them to Christianity, they gave them common Spanish names. The one name that is extremely common among the people around the Matagorda and Corpus Christi area is Rodriguez. I've met quit a few people from that area with the last name of Rodriguez that fit the general characteristics. Namely, most of their family members are well over 6ft tall, and there are stories amongst the families of being Indian.