I tweaked the map a little by adding 1,000 mile circles which is the absolute limit we should plan on for the majority of atendees. Even though there are some hardcore folks who'll make the long trip, 800 miles is about the realistic one-day limit for most, and it's the difference between two and four days of travelling on top of the convention.
800 miles = 14 hours @ 60mph average
1000 miles = 17 hours @ 60mph average
Add another hour or two in for convoy meet-ups, gas & food stops.