ERC suck for bonsai. I have grown them for multiple years early on, and they are disappointing. They get CA rust if you get near them with water, which lasts forever. You can control it, but not eliminate it. You will lose branches to it each year, big and small ones alike.
ERC also buds back strongly at crotches of old wood, but doesn't back bud well along branches, so you never get anything that resembles a good pad, you get clumps. They grow arrow-straight, and have horrible "memory", so wiring is never-ending. Add that to the growth habits, and it's very frustrating material for bonsai.
Do you have Ashe junipers or alligator junipers in OK? They're definitely TX trees, and would be infinitely better candidates. RMJ is also excellent. CA rust is controllable on them. I've managed to keep it at bay on mine since I collected them in 2013 using Daconil; even in my humid climate.