Deb and I looked at Bastrop State Park and the adjoining Buescher State Park. It is as remote as it needs to be and there are plenty of logging roads and some single track with hills. The only issue is that a good piece of these parks was ravaged by a forest fire and parts are still picking up debris and other parts look like the surface of Mars.
We have been looking for a state park tour south of Austin to take 3-4 days. We thought of starting at McKinney Falls SP, taking a road ride to Lockhart SP, then on to Palmetto SP just north of Gonzales. The ride between the parks is about 30 miles. this option puts you on the road more than it sounds like you want, but the scenery is nice, you can follow the San Marcos River part of the way and the barbecue in Lockhart is worth walking the trip barefoot.
Anyone got any improvement suggestions.