Half-mile (Lon Cooper) carried a GPS transponder while hiking the PCT last year. Besides measuring the mileage for the PCT, he also recorded many spur trails, including the MMWT from the peak to the Portal.
His mileage calculation is 10.4. You can access his maps and waypoints here:
http://www.pctmap.net/Here are the details for those interested in the technology behind the mapping project:
http://www.pcta.org/2014/ultra-high-tech-mapping-pct-long-distance-geo-logger-19469/
