When I was talking to Damian myself and asked him if he recommended supplementing the SDTS with anything else, he said that Judo, Sambo, even BJJ were good to train in also. He said that for the most part the SDTS modules 3 and 10 give you everything you need to know about groundfighting, throws, and takedowns but if you choose a martial art to pursue as a hobby or even to compete that those 3 were the best and had the most practical applications to real life situations that can occur on the street. He said a lot of the throws and takedowns from judo and sambo are good additions to the arsenal of takedowns we already learn in module 10. And that regarding BJJ, while we don’t rely on and try to avoid grappling when groundfighting and mainly just use weapons, biting, gouging, and striking to better our position to get back to our feet or finish him on the ground, he said that just rolling around on the mat and practicing escaping from and pulling off submissions and getting used to fighting and performing from a variety of positions in relationship to our opponent on the ground can help us get used to fighting from there and better aid us in being able to establish a dominant position over our opponent and better able to pull off the tactics given in the SDTS. Again, he said that the SDTS is a complete self defense system and gives you the potential and ability to deal with most any type of attack or altercation that can occur in real life, however if you simply wanted to train in a martial art either as a hobby, to compete, or simply supplement the SDTS that those three martial arts are the best.