Chad that launch from Dick's just below Whitney dam is anywhere from a 9-hour float to a Nantucket sleigh ride depending on the release. A nice overnight float is from Highway 7 bridge to Highbank. The only downside is I wouldn't leave a vehicle at either place, oh and you'll have to portage at the Falls (it's just a high water crossing. You'll pull out, walk 15 feet, and put back in). You'll need to have someone in a "hover pattern" waiting to pick you up at Highbank. You can camp on the gravel bars all along that stretch. I grew up along that stretch of the Brazos and can probably arrange a launch, a safe spot to leave your truck(s) at Mom's house in Pleasant Grove, and a pickup at Highbank. Just holler at me and we'll set it up.
"I have no idea what WW-III will be fought with, but WW-IV will be fought with sticks and stones."