The first mile or so from White's Crossing (FM 1871) is difficult or impossible to paddle under normal flows given the flutes; easy to see on Google Earth. So, there's not a lot of people who paddle that stretch.
I've done the South Llano from 2nd Crossing to Junction and the Llano from Junction to Yates Crossing. Junction/Yates is a great 3 day/two night float and 2nd Crossing/Junction is a great 2day/1night float when fishing. Yates Crossing (RR 385) to White's Crossing isn't a viable option either on normal floats due to the many miles of flutes which would require dragging, especially the last few miles. US 87 to Castell Crossing is a solid one day fishing float.
"Water is life's matter and matrix, mother and medium. There is no life without water." -Albert Szent-Gyorgyi
"No man ever steps in the same river twice, for it's not the same river and he's not the same man." - Heraclitus