Region IV stayed with the single SR judge until the 3-person panel was mandated by UIL. I started teaching in 78-79 and we always had a single SR judge. It was a region preference.
I went to my first marching contest as an assistant band director in Region IV in 1978. Marching contest was in Linden and Atlanta did corps-style. Made a II and the audience booed when the ratings were announced. The only time I remember the audience booing at a rating at a UIL marching contest.
I don't remember for sure but Frank Garza may have started doing corps-style at Liberty-Eylau a year or so earlier. And my dad did corps-style his last year in Daingerfield in 1979. Jim Keene, who was the band director at East Texas State University in Commerce was responsible for bringing the "gospel" of corps-style to Region IV. I remember my dad telling me about a road trip Jim did with several band directors in the summer of either 76 or 77. They drove a van up through the midwest and went to several DCI shows.
One of the other posters mentioned patterns in motion. We did that style when I was in college at SFA but I don't remember any Region IV bands that ever did patterns in motions style of drill. I could be wrong but I believe that was found more in west Texas and maybe other parts of the state. Our director at SFA had come from west Texas.