2 mph and 30 minutes extra per 1,000 feet??? You must be a flatlander. I don't know your experience, maybe I'm wrong, but I'm guessing you've never hiked any big peaks in the west. Because at that pace, you'd be hiking in the dark or in thunderstorms every trip.
At 240 lbs (nope, I'm not skinny), I usually maintain a 3 mph - 1,500 feet an hour pace. On cross country, I would say I slow to 2 mph. On straight up stuff, the distance part is thrown out and you should just look at the elevation gain. You should be able to gain 1,300 - 1,500 per hour.
My numbers jive with the pace of numerous hiking partners I go with, with the exception of one guy who is a goat and hikes at a pace about 50% faster than mine.