Mt. Mitchell Trail from Black Mountain Campground O&B - Black Mountain, NC.

I am considering doing the Mt. Mitchell Trail starting from Black Mountain Campground in two weeks when I visit WNC - http://www.hikewnc.info/besthikes/appalachian-ranger-district/mount-mitchell.

I've been reading that hikers take 3.5 hours just to go the 5.5 mi, and I'm wondering if anyone has run this 5.5 stretch and back. How long did it take you? I really want to try it, but also want to know how early I should start (considering mid-August).