About 10 yrs ago did unplanned completion solo (sort of see below). Road from Front Royal and planned to ride out eg 40-50 miles and back. Looked like storm approaching from North, so called my family, told them. Cont riding south to end; then on to Charlottesville where I was in school. Total was eg 120 miles. Storm never arose. Did not have keys to get into my apartment (hadn't planned to be there). Family very understanding and drove to CVille to pick me up from North of the Drive.
Don't recall any climbs on the Drive being too steep. It's the climbs onto the Drive from connecting roads that can be killer. The climb actually on the northern end from Front Royal is 5 mile, not steep, but long. Remember it well, b/c used to run up it.
Limited supplies.
Great views.
Have a great Day!!