I'll be making a trip from Clingman's Dome to Fontana Dam in April. I have an argument with my friend that says due to elevation change, we'll be walking more like 60 miles instead of 30. So what's the deal? I plan on spending 3 days on the trail and I expect to make it in that time. I realize that the hike will be strenuous and I've been training for it. Is 30 miles in 3 days unrealistic?