My starting assumptions for the 2010s map I'm doing:
Texas: total R control
Dallas: total R control turning into split control by 2018 (which effectively means an R quasi-dummymander I guess)
Galveston: total R control with slim R control by 2018 (effectively a moderate R gerrymander aimed at locking in seats in the 2010s)
Alamo: total R control turning into D control by 2020 (so effectively R dummymander)
Rio Grande: total D control with R vote sink drawn to keep Rs from winning anything else (probably mostly successfully but not completely)
Llanos: obviously this is the best turf imaginable for a D trifecta to form!