Wow I was just searching last night for Tejano Devils...to little success. I am very interested in seeing what happens. Personally I would leave them together, but watch them closely or at least periodically come back and check. He can't kill her with one blow.
My 5" Female hybrid Texas is kickin some Devils butts. 3 Red Devils in there with here, 2 are 1" bigger than her. I tried putting only one but he got so torn up I had to throw in his soldiers so the aggression/attacks are dispersed equally.