Coppertone and I arrived at Friedrich not entirely knowing what to expect in terms of the roughness of the terrain. Things were a little bit tougher than expected. In this case that was a good thing.
The Vista Loop on the back of the park provided the most undulating terrain and the fewest people. The parking lot was packed with cars though and one didn't have to travel far on the main loop before running into another set of hikers.
Our schedule and the heat didn't allow us enough time or energy to hike every mile of the park, so we'll have ample reason to visit again.