To escape the heat in GA in the summer, you will need elevation. Black Rock SP campground is 3400 ft up and as far as I know, is the highest CG in GA. (please correct me if I'm wrong ;). Not familiar with your TT, but Black Rock states a 26ft restriction mainly for the road up. Its a steep climb on a not so wide road.
They do have 3 or 4 sites that can go 30 ft and the hosts try to save those for the longer rigs. They claim cool evenings even in the summer and the CG is on a ridge with nice views a short walk away.
++My TT and truck are 55Ft long and are too long to negotiate inside the CG.