The NCAA calculator I downloaded give a 60s conversion for a 30:00 10k at 6000ft, but looking at distance of 1500-10000m it's apparent the longer you run, the more altitude slows you down PER MILE, so I'm wondering what the conversions are for 10 miles, half marathon, and marathon for high altitudes. I've lived and trained in cities both high and low, and I've found the pace I run for 4 miles at altitude is still a little slower than what I run for 10 miles at sea level. Anyone else with experience? Flagstaff/Boulder/Mammoth guys?