I live in a hilly area in the north of scotland. Like it or not I have no choice but to include some whopping hills on my circular road routes of 5 to 10 miles. I am training for a half marathon which is coastal so relatively flat. I currently run 7 min 30 a mile over a 7 mile course but this includes over 100m of ascent. Anyone know of a rule of thumb to take time off for height gained so I know roughly what I could achieve on a flat course?