Hey Leo,
We did the Hill Country about 6 or 7 years ago. The FM (farm to market) roads look like loose gravel but we found them solid. I was told that the tar shrinks and retreats in the winter. You dont see what is binding the "chips" but when the roads heat up in summer, the tar rises to the surface and can make the roads slippery. We were there in late Dec/Jan. All good advice above. Coopers is amazing, Willow city loop was fun but no blue bonnets when we went. We were told not to stop on the roadside in the loop as the local residents don't enjoy the extra traffic. We stayed at the D Rose Inn in Leaky, its a motorcycle resort. And look out for the small deer, especially at sunset.
Have a great ride!
Tom