Kudos to David Yerden for the idea of running from Kennesaw Mountain to Stone Mountain. Per his FKT post, I chose a different route that stayed further north in Atlanta and appeared slightly shorter with less climbing. That turned out mostly true with about 400 ft less vert but quite similar mileage (although that could have been because I took a few short wrong turns). I hiked up to the summit of Kennesaw before dawn and started around 6:45 a.m. There were several sections in the first half of the route (especially near Sope Creek) that didn't have sidewalks, but this was manageable with sparse traffic in the early morning. I made three stops for water at gas stations along the way. This alt route had mostly rolling terrain with climbing concentrated in the Sope Creek and the Brookhaven/Chamblee areas. I hiked to the top of Stone Mountain and touched the concession stand at around 11:25 a.m.
It was a very good day of running, and a really fun route to try out. And I didn't realize this, but you can see Kennesaw Mountain from the top of Stone Mountain, which was a cool way to visualize everything.