20/day, you might have trouble finding camping spots. 50/day, I think you might be okay. First time I went from Raleigh to the Outer banks, I kicked it off with an 80 mile day, which was doable, but not pleasant for me by the end of the day, and it set me up for a rough second day, even though the second day wasn't as long. The next time I did it in 60 mile sections, and it went much more smoothly. If you're willing to stealth camp, 50 miles is likely doable. If you're looking for campsites, it might still work, but it might involve a little zig-zagging and adding a day or two to your trip. But if you have the time, take it easy. My first trip out was far less pleasant than my second one, mainly because I felt like every day I was racing daylight to my campground.